Prorated refund after canceling service turned into false balance. How do I get this rectified?

This has been the most frustrating off-boarding experience ever. I canceled my Comcast service on 11/11. I was billed and I already paid $134 on 10/31/24 for the following month’s service (Nov 5 - Dec 4 service dates) because all of Comcast's invoices are for the next month’s service, and the bill itself says that I paid for the Nov 5 - Dec 4 service dates.

I should have receive a prorated refund of +$107.20 for canceling my service on 11/11/24. I even have a screenshot of my account from the app that says I was due this amount. Instead, after the month finished, the balance on Comcast's website says now that I owe $26.80, which is incorrect, given that I already pre-paid for the Nov 5 - Dec 4 service month, and canceled on Nov 11. Basically, the website took the *next* month's bill ($134 for Dec - Jan) and subtracted $107.20 from it to get the $26.80 balance. But I had already pre-paid for the Nov 5 - Dec 4 service dates, so I am actually owed the $107.20 balance. I don't need to pay for Dec - Jan service because I canceled my service in November!

I tried explaining this to a chat agent and they kept saying that I owe the $26.80 balance. They contradicted themselves by saying that Comcast always bills *in advance* but that 'I paid for the Oct - Nov service month'. That doesn't make sense. I have written proof and screenshots that show that I pre-paid $134 for the Nov 5 - Dec 4 service dates, and that I am owed +$107.20.

How can I get someone to actually understand that my account has a false and fraudulent balance of $26.80 that Comcast says I owe — when in fact that Comcast owes me a +$107.20 prorated refund for canceling my service on 11/11 after prepaying for that entire month? Thanks for any guidance here.