Rental Equipment is a Total Scam

I purchased a tv and internet bundle in March 2021. This service was a 12 month agreement. In April 2022 I canceled this service and have documentation verifying cancellation. I then agreed to a new service of just WiFi which is a totally different agreement. I gave the inactive to my husband to return and unfortunately he lost or forgot to do so. Now according to what I am finding online xfinity should have charged me $150 for each unreturned equipment. They did not and they continued to charge me rental fees until April 2024(I had automatic payments and did not realize). So they charged a total of $480 for inactive equipment instead of $300. I then complained online and took screenshots of the chat. The worker who helped me sent over an updated contract with the inactive equipment removed which I signed. She also said she was going to put in a claim for me which never happened. A month later I get a bill with the inactive equipment back onto my bill. So I complain again. The person who helped me this time admitted Xfinity was at fault and then said he could fix it if I agree to a plan that was a 1 year term agreement. Xfinity rental equipment is a total scam! How does a charge get added back onto my bill without consent after I have an agreed upon update to service where it was removed?  I really want to cancel my contract and move to ATT but am scared of getting charged an additional $300 ontop of what I have already paid.