Xfinity Mobile line blacklisted

I transferred my Mint mobile line to Xfinity 3 months back and was supposed to get a $400 credit. I got the credit in the first month but the issue started in the second month. I started seeing a secondary phone on my line. I lost my promotional credits starting this month. Then, I tried contacting Xfinity support but they couldn't do anything about it and kept me waiting for months. Then, I asked them to unlock my phone which was when issue started and they reported my number and device as lost/stolen. Since then I have had no service. It already has been more than a week and they just keep giving further dates.