How to make a formal complaint about the lack of proper customer support, communication to customer and no follow-through

I have two accounts for a year and a half already and had the one account since 2015, so it was a no brainer to continue and transfer my plan when I moved leaving me with two accounts with xfinity. The monthly premium has increase for both accounts twice, with no prior notification. I don't receive the invoices because they are online, and they are not clear so I can't see what happening. I haven't had any internet in one of the properties since last April (which I don't live at it's only for a DVR). I spoke to someone on April 23 to disconnect the service and see if I can get a refund for at least some of the months I understand not all the month- then they said as a fix for the issue they would put me on a seasonal account. So two tickets were done 3 hours on the phone total (had to call 3 different time). So that I dont disconnect they said would refund me $360- they aren't able to refund the full year of no service no usage which I understand. No one ever called me to follow up and on May 1st they deducted $105.99 this month regardless that I had called about not having any internet regardless they discontinued services and placed it on a seasonal hold.... I called about it this morning, again asked them to disconnect my account because I'm done with the games, only to find out that they never placed the account on a seasonal hold, they want me to fit with my bank to claim the money back and they closed the refund unresolved because the person that placed the escalation ticket didn't respond to their question.. So basically no one knows what they are doing I've spoken to 4 people all in different  countries, just now spoke to someone from the US and still no resolution - she said I have to reopen the tickets - I ask her to please reopen the tickets and she said no she couldn't that I have to call back - no one in Xfinity knows what they are doing, no one knows how to effectively communicate or effectively provide good customer service.. It is outrageous. It is mind-blowing what these people are doing, and I'm convinced that they do it on purpose, so you just give up and forget about it or leave it alone.. Well, the 300 they were getting from me a month and the 350 from my mom, they are going to lose because this is unacceptable.  I've spoken to 5 ppl an hour long with the first three service reps, 30 minutes with the last two one being a manager who said they would refund me, and he would call me back directly and nothing that has been said or promised or follow up has been made the service specifically customer service is horrendous, subpar to say the least. I hope they continue to lose customers.  They are really quick to take your money and snakingly increase the rates but can't have the same follow through with customer service. How sad.