Check the Recently Deleted folder in Messages
Open Messages
Tap Edit or Filters
Tap Recently Deleted
Select the messages
Tap Recover
Restore from an iCloud backup
Go to Settings
Tap General
Tap Transfer or Reset iPhone
Tap Erase All Content and Settings
Set up iPhone again
Choose Restore from iCloud Backup during setup
Restore from a computer backup
Connect iPhone to a Mac or PC
Open Finder or iTunes
Select your iPhone
Choose Restore Backup
Check other Apple devices using the same Apple ID
Open Messages on iPad or Mac
Look for the deleted messages there
Ask the sender to resend the messages
Contact your carrier if SMS backups are available
Use a third-party data recovery tool if needed