Check the Recently Deleted folder in Messages
Open Messages
Tap Edit or Filters
Tap Show 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
Restore from a computer backup
Connect iPhone to a Mac or PC
Open Finder or iTunes
Select your iPhone
Choose Restore Backup
Pick a backup made before the messages were deleted
Check if Messages in iCloud is enabled
Go to Settings
Tap your name
Tap iCloud
Tap Messages
Turn it on if needed
Contact your carrier
Ask whether SMS backups or message records are available
Use a third-party iPhone data recovery tool
Scan the iPhone or backup
Recover deleted SMS if the tool finds them
Check other Apple devices signed in with the same Apple ID
Open Messages on iPad or Mac
Look for the deleted SMS there
Sync messages if needed