Check the Recently Deleted folder in the Messages app
Open Messages
Tap Edit or Filters
Tap Show Recently Deleted
Select the messages you want
Tap Recover
Restore from an iCloud backup if the messages were deleted earlier
Go to Settings
Tap your name
Tap iCloud
Check iCloud Backup
Erase and restore the iPhone from a backup that contains the messages
Restore from a computer backup if available
Connect the iPhone to a Mac or PC
Open Finder or iTunes
Restore from the backup that contains the messages
Check other Apple devices signed in with the same Apple ID
Open Messages on iPad or Mac
Look for synced conversations
Ask the sender to resend the messages
Contact your carrier if SMS backup or message recovery is offered
Use a third-party recovery tool only if you trust it and understand the risks