I need help to retrieve text messages I deleted on accident

That depends. If you sync your texts to iCloud, then they are not recoverable. If you do not sync to iCloud and you have a backup to either iTunes or iCloud that contains those messages you can restore that backup. Note that restoring a backup is all or nothing; it replaces all of the content on the phone with the contents of the backup. It isn't selective.

To check if you are syncing to iCloud go to Settings{your name}/iCloud and check the switch for Messages.