Whatsapp not only test the mobile IMEI numbers but also test the valid or wrong numbers.
suppose if you have entered a invalid/wrong number.
To test this,you need to have a mobile with SIM inserted and whatsapp installed and with minimum balance.
Then the procedure will be as follows:

1. Launch the application.
2. Enter any number other than your mobile number and tap on “OK” button.
3. Verification process continues and after 10 minutes of total time.
4. Your mobile gets “connection failed,reverify” popup.

This will happen because whatsapp will work for one number and one device.
If any one try to register with a invalid/wrong number,a highly secured procedure is implemented.

Here in this you are going to see how whataspp will work when given a other number in the verification process.
For this,you need to have two mobiles with SIM inserted and with minimum balance.
And also the whatsapp need to be installed in both mobiles.
The following are the steps to verify:

1. Install the application in mobile A.
2. Launch the application.
3. Enter the mobile B mobile number and tap on “OK” button.
4. Again after 5 minutes,mobile B will receive a message from Whatsapp server which contains 6 digits code.
5. After the total time(10 minutes),Displays a popup showing “SMS verification has failed,continue voice verification by calling the entered number”.
6. After tapping on “call me” button,again a popup appears with “Enter code here” field.
7. As soon as we tap on “call me” button, a call from Whatsapp server will come to the entered number.
8. This call will continue till we attend the call.
9. If the call was answered,a 6 digit number will be heard by voice.
10. If we enter the 6 digits code which was heard,The mobile A gets registered with the entered number and call gets automatically disconnected.
11. Otherwise if we enter the 6 digits code which was received as an SMS, the mobile A gets registered with the entered number. I,e. mobile B mobile number.

Here the mobile B will get the balance deduction,since mobile A has entered its number.
All the people in the mobile A whatsapp contacts list a ableto mobile B mobile number only.
So by this it is observed that whatsapp will consider only the IMEI of the application installed mobile and a valid number(even though it is not inserted in same mobile)

Here in this you are going to see how whataspp will work when given a other number in the verification process. (other number in the sense mobile which is not a smart phone)
For this,you need to have two mobiles (one is a smart phone and other is normal phone) with SIM inserted and with minimum balance.
And also the whatsapp need to be installed in mobile A(smart phone).
The following are the steps to verify:

1. Install the application in mobile A.
2. Launch the application.
3. Enter the mobile B mobile number and tap on “OK” button.
4. After 2 minutes,mobile B will receive a encrypted message from the mobile A mobile number.
5. Again after 5 minutes,mobile B will receive a message from Whatsapp server which contains 6 digits code.
6. After the total time(10 minutes),Displays a popup showing “SMS verification has failed,continue voice verification by calling the entered number”.
7. After tapping on “call me” button,again a popup appears with “Enter code here” field.
8. As soon as we tap on “call me” button, a call from Whatsapp server will come to the entered number.
9. This call will continue till we attend the call.
10. If the call was answered,a 6 digit number will be heard by voice.
11. If we enter the 6 digits code which was heard,The mobile A gets registered with the entered number and call gets automatically disconnected.
12. Otherwise if we enter the 6 digits code which was received as an SMS, the mobile A gets registered with the entered number.i,e. mobile B mobile number.

Here the mobile B will get the balance deduction,since mobile A has entered its number.
All the people in the mobile A whatsapp contacts list are able to see mobile B mobile number only.
So by this it is observed that whatsapp will consider only the IMEI of the application installed mobile and a valid number(even though it is not inserted in same mobile)

Here in this you are going to see how whatsapp will work when given a already registered mobile number in the verification process.
For this,you need to have two mobiles with SIM inserted and with minimum balance.

In these mobiles,mobile B is already registered with whatsapp and mobile A installed but not registered.
Now just follow the steps to verify:

1. Install the application in mobile A.
2. Launch the application.
3. Enter the mobile B mobile number and tap on “OK” button.
4. Again after 5 minutes,mobile B will receive a message from Whatsapp server which contains 6 digits code.
5. After the total time(10 minutes),Displays a popup showing “SMS verification has failed,continue voice verification by calling the entered number”.
6. After tapping on “call me” button,again a popup appears with “Enter code here” field.
7. As soon as we tap on “call me” button, a call from Whatsapp server will come to the entered number.
8. This call will continue till we attend the call.
9. If the call was answered,a 6 digit number will be heard by voice.
10. If we enter the 6 digits code which was heard,the mobile A gets registered with the entered number and call gets automatically disconnected.
11. Otherwise if we enter the 6 digits code which was received as an SMS, the mobile A gets registered with the entered number.i,e. mobile B mobile number.
12. Then mobile B will gets “connection failed,reverify” popup.

This will happen because whatsapp will work for one number and one device.
If any one try to register with already registered number,a highly secured procedure is implemented which will protect the user from unauthorised persons.

Earlier there use to be only single SIM phone.
But when the technology has improved,DUAL SIM phones came in to existence.

Now in this post, am going to explain how whatsapp works on a DUAL SIM phone.

Now just follow this procedure…

But before this you need to have the two SIM cards inserted in your phone.
Now for the explanation, I considered SIM1 as permanent number and SIM2 as temporary number.
If I want to register my SIM1 with whatsapp application,then

1. Launch the application in your phone
2. Enter SIM1 number and tap on “OK” button.
3. Verification process will completed in 10-15 secs of 10 minutes total time.
4. Your phone will get registerd with its own SIM1(mobile) number.

Suppose if i want to change my number to SIM2,then

1. Launch the application in your phone.
2. Tap on change phone number option in settings.
3. Enter the “old phone number(SIM1)” and “new phone number(SIM2)” in respective fields and tap on next button.
4. Again the verification process will continues.
5. Again after 5 minutes,your phone (SIM1) will receive a message from Whatsapp server which contains 6 digits code.
6. After the total time(10 minutes),Displays a popup showing “SMS verification has failed,continue voice verification by calling the entered number”.
7. After tapping on “call me” button,again a popup appears with “Enter code here” field.
8. As soon as we tap on “call me” button, a call from Whatsapp server will come to the entered number.
9. This call will continue till we attend the call.
10. If the call was answered,a 6 digit number will be heard by voice.
11. If we enter the 6 digits code which was heard,your phone will get registered with the entered number and call gets automatically disconnected.
12. Otherwise if we enter the 6 digits code which was received as an SMS,then also your phone will get registered with the entered number. i,e. Device A SIM1(mobile) number.

But the SIM2 gets unregistered.
As whatsapp will work only in one device with one sim.
Here it considered the second scenario as one device with dual sim i.e,different IMEI numbers will be present for DUAL sim mobiles.
At first it considered SIM1 but when try to change to SIM2,then verification process continued.

In the first post you have seen the registration process using your own mobile number.
But in case, if you want to change your mobile number(because of any reason).
Then no problem you can continue with whatsapp using your new mobile number.
All you need is follow these steps:

1. Switch OFF your mobile,
2. Remove the registered SIM card and insert a new SIM card.
3. Turn ON the mobile.
4. Launch the application.
5. Application will work as before(connected to WiFi/Mobile Data connectivity).

All the people who are in your whatapp contact list are able to see your old mobile number only.
And if any one send you a message,you will able receive it as usual.
This scenario will work fine until you uninstall and install the app.

In case,if you have uninstalled the whatsapp application,
Then the following procedure will continue…

1. ReInstall the application.
2. Launch the application,again the verification process popup appears.
3. Enter the new mobile number of the inserted SIM and tap on “OK” button.
4. Verification process will be completed in 10-15 secs of 10 minutes total time.
5. Your mobile will get register with the new mobile number.

But the removed SIM will get unregistered which means that no mobile is using the number and can be used again.

Here we are going to see how whatsapp works when two registered mobile numbers(SIMS) are interchanged.
For this you need to have two mobiles registered with their own mobile numbers.
Now to verify the above scenario,follow the procedure:
But you need to connect to a WiFi/mobile data.

1. Switch OFF both the mobiles A & B.
2. Remove both the registered SIM cards from mobile A and B.
3. Insert the SIM card of mobile B in mobile A.
4. Insert the SIM card of mobile A in mobile B.
5. Turn ON mobile A.
6. Turn ON mobile B.
7. Send a message from any other mobile to mobile A removed SIM number.
8. Message will come to mobile A only, even though it is using mobile B SIM.

By this it is observed that whatsapp will work even though the SIM card is changed/removed.
But this scenario will work untill we change the number in “change number” option in settings or if we uninstall and reinstall the application.

There are a lots of smart mobiles in the market.
Some support only GSM (or) both GSM and WCDMA(3G)
But there are others which do not support/work on any GSM network world wide.
i,e.which is not a GSM device.
Some of them are Karbonn Smart Tab2(ST2),(ST7),(ST8),(ST9),(ST10).
Suppose if you had any of the above tabs,don’t think that you are away from your friends.
whatsapp will also work on these devices(tabs).
All you need is to follow the below procedure…
But before that you need to have a other mobile with a SIM card, and your own smart tab

1. Install the application on your tab
2. Launch the application
3. Enter the mobile number (in which whatsapp not installed) and tap on “OK” button
4. After 2 minutes,mobile B will receive a encrypted message from the mobile A registered SIM1(mobile) number.
5. After 5 minutes,the entered mobile number(device) will receive a message from Whatsapp server which contains 6 digits code.
6. After the total time (10 minutes), it displays a popup showing “SMS verification has failed,continue voice verification by calling the entered number”.
7. After tapping on “call me” button,again a popup appears with “Enter code here” field.
8. As soon as we tap on “call me” button, a call from Whatsapp server will come to the entered mobile number.
9. This call will continue till we attend the call.
10. If the call was answered, a 6 digit number will be heard by voice.
11. If we enter the 6 digits code which was heard, Your smart tab will get registered with the entered number and call gets automatically disconnected.
12. Otherwise if we enter the 6 digits code which was received as an SMS, Your smart tab will get registered with the entered number.

Now you can stay connected with your friends using whatapp in your smart tab.
Your friends will able to see your entered registered mobile only.

Cons: There should be an user interface in whatsapp menu to add a contact(phone) manually.
which is a drawback in whatspp when installed in a device which does not support GSM Network.

First you need to have Application installed in your mobile and needs to have minimum balance.

Follow the steps:
1. Install the application.
2. Launch the application.
3. Enter your mobile number and tap on “OK” button.
4. Verification process will be completed in 10-15 secs of 10 minutes total time.
5. Your mobile will get register with your own SIM(mobile) number.

Suppose if the application was uninstalled, you can again install and register with the previous number.
The process will be same as the above.