Incorrect Billing and no one to speak to or chat with online.

I no longer have xfinity service as of Oct 30th 2020. I moved. I also walked into one of the stores and returned all the equipment. The store in early Nov. confirmed all equip. was returned and there were no balances on my account. I then several months later get billed for some unknown equipment charges of about $45. Now there is no one to speak with or email. No matter how hard i try to contact them directly i get put on hold for hours. The online chat just goes in a circle and says due to Covid I need to contact a 1-800 #.  But when i tried it takes hours. I did finally did get a person to call back but after 45 minutes we got disconnected. I personallhy think she hung up. Abigale was her name and she never called back.  I just need the charge removed. After 16 years of service with xfinity/comcast I would think I would have gotten better service than this?   Any suggestions?