Check the Recently Deleted folder in the Messages app
Restore your iPhone from an iCloud backup made before the messages were erased
Restore your iPhone from a computer backup made before the messages were erased
Use Messages in iCloud if it was enabled on your device
Ask the sender to resend the messages
Contact your carrier to see if message records are available
Use a third-party iPhone data recovery tool
Check other Apple devices signed in with the same Apple ID
Verify whether the messages were archived in another app or account
Contact Apple Support for recovery options