This question has been asked WAY too many times. I reckon you should check those answers out before asking again, or asking at all!
Sometimes , even you think you did not backup the lost data before, I still suggest you check your most recent iTunes or iCloud backup.
But if that doesn't help either, you can use data recovery tool to recover deleted text messages iphone.
Hey, you can look at this video:
Hope it helps!
Bitwar iPhone Data Recovery is a professional apple Recovery master, it can help you recover