how can i get a billing issue resolved when I am being charged after no longer having the equipment to make calls and they refuse to help

Back in August of 2025 I called Comcast and told them I was porting my business office phone number that I have had for over 20 years to an ATT cell phone for way less money. They gave me some options but since I have been with ATT for my personal cell service since forever I declined their offer and asked what do I need to do to terminate my service and I was told to return the equipment to a UPS store and save the receipt and that was it. I owed about $ 185 at that point. I returned the equipment as soon as the port with ATT was done which was 9/26/2025 as per the receipt from UPS store. I called Comcast around October I believe because I kept getting bills and I wanted to pay the amount owed and when I called Comcast customer service I was told since I didn’t sign a form to cancel service which I was NEVER told I needed to do because trust me this would have avoided all these issues, they told me I needed to wait till the service was disconnected due to non payment to then pay. Makes no sense whatsoever. Mind you I had no way of having service because the equipment was returned on 9-26-2025 but they don’t acknowledge that at all ever. So, when I did call back sometime in December I believe I was told I owed 901.26 through end of November for service even though I had no equipment and my number had been ported since August 2025. Amazing. I told them to bill me till the equipment returned date and I would pay that but not more because I had no equipment and they said no. At this point I gave up. I was sent on every call back and forth to every other department no less than 10 times and honesty no one has that kind of time when you are trying to run a business. I also had some medical issues with my parents and I forgot to call Comcast back. Now comes July 7th, 2026  and I get a text from ATT that I have a porting issue and I need to contact them or lose my number that I have had for over 20 years mind you. I was on the phone with ATT and Comcast on 7-8-2026 for over 5 hours total and nothing was resolved. Comcast said I need to pay the whole amount and they will not give me credit and ATT is asking me to work with Comcast to get my number back. I only spoke to one person at Comcast that offered to credit me back to 9-26-2025 and she said she needed to transfer me to another dept to get authorization, and the next person said no. I asked for supervisors and was told the same thing. Honesty this is why I left Comcast. Their customer service dept is terrible. Conclusion of this long-winded story is I need my number back and now. Please help me find someone at Comcast that can give me my number back. I am willing to pay to the date of 9-26-2025. It is not my fault I was not given correct instructions on how to cancel my service. Training on the Comcast side needs to be better to make sure people get the correct information. Please HELP! I am missing phone calls and I am not compliant with my home office. HELP