How do I file a complaint about Xfinity and Assurant

I have been fighting with Xfinity and Assurant for weeks. My phone stopped working. I filed a claim because I have been paying for protection for years. Assurant says my carrier has to fix it then Xfinity says Assurant has to fix it. Meanwhile, I had to purchase a new phone without using my old phone as a trade-in. My bill has gone from &140 to over $300. This is crazy. Maybe I should get a full refund for the protection plan I’ve paid for. To whom do I speak?? I am beyond angry.