i'd be looking to restore the phone with a fresh OS. just like a pc, blowing away the OS and installing a fresh one is a good idea.
http://www.galaxynote5update.com/galaxy-note5-stock-firmware/
once done i'd update the PRL, ATT network baseband and anything else you can update. should wipe out whatever was done to the phone. won't stop it from happening again if someone is determined but at least it'll be safe until the new phone comes in. sucks but i'd be asking for a new phone number as well, if you got a psycho stalker messing with you.