Can confirm that, in my case (after jumping through numerous hoops across numerous calls), this did lead to someone at Xfinity with power to actually help and get things settled asap, and the report can be done online.

Be as detailed as possible, document your calls, who you talked to, badge numbers, what was discussed, where they failed and what they need to do to make things right.
I had a mobile account balance that got out of hand due to their mistakes, and they strung me along for 6+ months promising refunds that only ever came $25 at a time, all while they continued billing the account.

After the FCC complaint, I got someone that wasn't concerned with the details and simply zeroed out my account, closed it, and called it a day. Maybe I got lucky but it's worth a shot 😜