Phone Reported Stolen but It's NOT Stolen - How do I restore service

This is a second post - I have not resolution yet and am desperate. I purchased a new iPhone and out of the blue it was suspended. I called ATT and they said someone reported my son's phone stolen when it wasn't. I reactivated the phone when ATT shut it down -the status was "suspended/stolen." I walked into ATT to prove that we have possession of the phone and they restored it. The phone disconnected 2 days after I called customer service and they launched an investigation. They restored it again. but a month later it was shut down again. How do I STOP my phone from being shut down? It's not stolen and I am tired of the back and forth with ATT. Can you just give me a new phone? Obviously, someone is fraudulently reporting this phone stolen and this is irritating.  Or ATT has a glitch in their system. It keeps getting turned off after a few days! What is the permanent fix in this situation?!