My answers below, but for your current issue, put in a complaint with the FCC or email the CEO of the company directly. Most major companies have a process to resolve issues that normal agents can’t access if you can get to the right level. Emailing the CEO works with many companies, but telecom companies are sensitive to FCC oversight and would rather fix your issue than deal with the FCC.
Yes, the agent agreed with me that the company owed me money, but told me they couldn’t do anything about it. I told them I understood, but please put in a ticket to someone that could do something about it. They just kept telling me they couldn’t help until I got mad. They eventually relented and put in a ticket, which was then denied without reason a month later. I resolved the issue by circumventing the call center entirely and getting directly to an escalation team similar to what I recommended above.