How to file a complaint

I have tried many times to get my bill corrected by chat, phone call and visiting the store, and it still has not been resolved. I am desperate to talk to a real person who can really help me. The issue is that there are three accounts at the same address, two houses and a tiny house. When the person who added service to the tiny house, she apparently has a balance due from a previous address that was added to my bill. I chatted with someone from Xfinity that said it would be corrected, but it wasn’t. So I went down to the local Xfinity store and they said that they couldn’t help me and to call customer service. I was literally on the phone with customer service yesterday for four hours getting forwarded from one department to another but nobody seemed to fully understand the issue and nobody helped me. I finally said that I had to get off the phone but was assured that they would give me a call back when the issue was resolved, but of course, no call back. What does it take to talk to a competent person who can take this balance forward off of my bill that is not mine?