If you’ve changed phone numbers but kept the same phone, you
don’t need to uninstall and reinstall
WhatsApp just to change numbers. There’s a setting
within WhatsApp that
will let you migrate your WhatsApp account to a different phone number.
Go to
Settings > Account > Change number. Enter your old phone number in the top field and then your new phone number in the bottom field. Then press
Done. Verify your new phone number, and all your chat history, groups and so on will be migrated to the new number