Please advise on how to speak to someone in upper level management

Going back almost 18 months now, I have been trying to get this issue resolved.  I have submitted more tickets than I can count and still have no results. I purchased fiber in November of 2023 to replace my then regular comcast business internet and my sales rep never submitted the ticket to cancel my existing internet service. After emailing her and her supervisor for over 7 months, I finally received her response stating she had dropped the ball and she was sorry. After that (45 days later) I received the docusign email to cancel the old business internet (keep in mind it still drafted from my account each month along with the new fiber bill at all of my offices) and I signed the request then comcast cancelled my fiber, which disrupted my operations for over a day. And as the story goes, so on and so on....  Here we are almost 2 years later and I'm still trying to get this resolved. I've spent at least 2 weeks of my time on the phone with comcast business support over the last 10-14 months, spoken to around 150 reps and each time, each rep says the same thing," I will have to talk to a manager". They get my info and say a supervisor/manager will call me and I still haven't spoken to one. I'm owed a very large refund and yet I'm receiving past due bills along with collection letters even though my fiber bill drafts monthly for all my locations. I would like the compliance office or the division where I file a formal complaint.