Email from Xfinity threat to send an incorrect bill to collection agency

My Xfinity internet service ended 3/17/2024. On 3/11/2024, I made a phone call to cancel our service, and returned the equipment on 3/24/2024. My actions should not generate any additional charges. However, early Apr, I received a message stated Xfinity is scheduled to draft $122.05 out of my checking account for 3/18 to 4/17 - the period I do not even use the service. I immediately called customer service and help them figure out the timeline and math. She said not to worry and would refund me the money if it is processed. My gut told me not to trust her, so I turned around and called my bank to block Xfinity to auto draft my account (I cannot even remove my bank info from Xfinity after canceling my service- is it even legal?). On 04/11/2024, they tried to auto draft the payment and failed.

After that, I got an email saying I needed to pay the amount to avoid late fee. I was furious as I thought my phone call has resolved the issue. Therefore, I called again and explained the situation. I walked through the timeline & math. The representative agreed with me and told me to ignore the email and not pay anything. I asked her to write me an email stating that I do not owe any bill, but she said she could not, and I just had to take her word for it.

Today, I received a bill stating that I still owe $53.64. They charge me service fee from 3/17 - 3/24, the period I already cancel the service plus equipment return fee ($30). I know that I have 30 days to return the equipment, free of charge. Therefore, this bill is not right. Additionally, I received an email threat to hand this bill to a collection agency if I do not pay ASAP.

This has been a very unncessary mental stress to me. I am currently 35 week pregnant and all I want is to move on and be mentally healthy for my newborn. I am running out of options and do not know if I need to take other actions to let Xfinity leave me alone.