My previous sim is expired. And I have already registered to new number. Is there any way to transfer previous details (groups and chat history) to my new number.I have no backup.
There are two situations which decides the outcome to this.
1> Even though your sim card has expired, you still have whatsapp signed in on the phone with the expired number and is still accessible. 2> You have uninstalled whatsapp after sim card deactivation.
In case 1, just go to settings and select change number and change over to the new number. All your existing groups and chats will migrate sucessfully in this case.
If it is case 2, there's nothing much that you can do.