Returning a 7 month old phone

My phone broke after 7 months. I returned the phone...no damage. I had a screen cover and a protective cover. I am 76 years old and have never abused the phone. Xfinity has the ability to rate the phone on what they perceive as wear. A grade from A to D is assigned. The customer is given no opportunity to dispute the grade. In addition to having to pay almost the entire price for the new phone, they added I sultan to I jury by charging me a restocking fee of $35. What are my options to dispute this. It is all sorts of wrong and seems to border on fraud.