Ensure that you’ve enabled auto chat backup in WhatsApp. To confirm this, go to Settings > Chats > Chat Backup within the app.
2. If you know the date of the last backup, remove WhatsApp from your iPhone and redownload it from the App Store.
3. After installation, launch WhatsApp and confirm your phone number.
4. Select the “Restore Chat History” option from the screen.
5. After the restoration process is finished, the deleted WhatsApp messages on your iPhone will be visible.