MTN IS NOT ASSISTING ME WITH PROOF OF OWNERSHIP FOR MY PHONE

Three years ago I took an iPhone 15 Pro Max on contract with MTN. The phone was ****** two weeks ago and my insurance wants the proof of the contract or anything that will serve as proof that the phone was under my name and belonged to me. I have went to MTN shops asking for help and they tell me I can only get assistance if I phone in but when I call in they tell me I need to go to a branch. Can someone please help me!!!