Before you stop using a particular phone number, you should migrate your WhatsApp account to the new number. For a simple way to do this, use our Change Number feature. By using this feature, you will be able to migrate your account information (including your profile information) as well as your groups.
Make sure your contacts delete your old phone number from their phone's address book and input your new number. As it is a common practice for mobile providers to recycle numbers, you should expect that your former number will be reassigned.
Note: You do not need to delete your old account. After successfully using the Change Number feature, your old account will be automatically deleted.
If you are moving from one type of phone to another, such as from an iPhone to an Android, and preserving your number, you will keep your account info. This information is tied to the phone number. Simply download WhatsApp on the new phone and verify your number.
Note: You cannot migrate your messages across different types of phone.
If you are moving from one type of phone to another and not preserving your number, simply download WhatsApp on the new phone and verify the new phone number.
Important: Remember to delete your old account. However, if you did not delete your account and no longer have access to your old phone, do not worry. If the new owner of your old number activates WhatsApp on a new phone after 45 days, all of your account information tied to that phone number will be completely deleted.
If you are moving to the same type of phone, such as from an Android to another Android, then you may have an option to migrate your messages. Learn more about transferring your chats on: Android | iPhone | Windows Phone | BlackBerry 10
Before you give away your old phone, make sure to wipe it of all your data. Remember also to wipe the SD card, if applicable. This ensures that none of your private data, such as your WhatsApp messages, will fall into someone else's hands.