Check the Messages app conversation list for recently deleted threads
Open Messages and tap Edit or Filters, then check Recently Deleted if available
Restore deleted messages from Recently Deleted within the retention period
Restore your iPhone from an iCloud backup made before the messages were deleted
Restore your iPhone from a computer backup made before the messages were deleted
Check other Apple devices signed in with the same Apple ID for synced messages
Ask the sender to resend the messages
Contact your carrier to ask whether message records are available
Use a trusted third-party iPhone data recovery tool if no backup exists
Turn on Messages in iCloud and regular backups to prevent future loss