Note that once you lose data like SMS on Samsung phone, whatever it’s Galaxy S7 or Galaxy S8, STOP USING your device in case that the deleted content be overwritten and gone for good.
After Data Loss Happens
Though files can be retrieved once deleted by accident, there is still a chance that they might be gone forever. Space on internal memory that were once taken up by the deleted files may be occupied by the new-generated data. So the first thing you should do after losing data is to stop using the Samsung device until you recover the messages with Android SMS Recovery.
FBI didn’t get the memo.