support Phone number held hostage

Came to Xfinity mobile several months ago. Brought my own Iphone. That phone was destroyed. Bought new phone from Xfinity, started making payments. I keep getting billed for service that I dont and havent used. That phone was also destroyed into a million pieces sim card too. I contacted xfinity multiple times to help with another phone. I get hour of run around to tell me they want money. I say bill me they say they cant. My phone number has been held hostage now for like six weeks. I can not afford to pay for a new phone when paying on one already. I explained to bill me and after many many years with comcast Im told there is no credit. I filed for an insurance through assured I have a plus plan im paying on as well and now told I still need to pay 99 dollars. I asked for a cheap phone free or something to get my phone number back. No help. Ive tried multiple old phones including ones that were with service and cleared port and id but still told incompatable. How the heck am i suppose to fix this