Looking for $3k refund for Xfinity mobile service that I canceled and never used but was charged for

Hi - So I originally signed up for Xfinity wireless mobile phone service in June 2022 as I was trying to save a little money as I have Verizon wireless. I decided when I got Xfinity Wireless to cancel it and I never used it. I was solely using my Verizon Wireless for three phone numbers. I thought it was canceled and never really thought about it until November 2023 when I was going over my bank account and autopays and noticed a charge of $200 for Xfinity, which I found I had been charged since August 2022, so we are talking about 18 months at around $200. After discovering the issue, I called Xfinity in November 2023 and a customer service person spoke to myself and my wife and acknowledged this was a big problem and that I should be refunded for this and was told I would get an update in 5 to 7 days. The customer service agent saw that I never used the service (how could I use Verizon and Xfinity at the same time with all the same numbers) and I believed I was going to get a refund. Now its mid January and myself and my wife have to spoken to Xfinity for at least 15 hours over probably 10 phone calls and yesterday they told me they are refusing to refund the money. They said they would basically give me $200 for one month and they wanted me to accept that. They claim that they have no record of my cancellation, but I know that I called and canceled. I'm pretty much speechless because Xfinity charged me $3000 for a service that I canceled and never used, but the customer service folks won't give me my money back. I really don't know where to turn at this point, but I'm super disappointed in Xfinity (Comcast) as I was a long time customer of their cable service. If there is anyway to help me rectify this situation I would be forever grateful. Thanks much for your consideration. [Edited: Personal Information]