Being charged for a phone line I did not purchase

In March 2026 I canceled internet service provided by Xfinity, I kept the credit card open for the auto payment to cover any closing costs. I was charged $44.10 for a mobile plan i did not purchase, after reporting it Xfinity refunded me $44.10 as there was zero usage and assured me that the line was closed and my card would not be charged for anything else. Before I close the auto payment, my credit card was chaged for $76.51 on June 7th 2026 for the same mobile plan. After an hour speaking with various agent the only way the plan could be canceled is if I sign on another plan, I told them I am not comforatble with this, I want my refund of $76.51 and cancel the mobile plan I didn't sign up for. The agent said she credited my account and i will see the refund back in my card with in next 5-7 working days. It is not more than 7 working days, I do not see any refund on my credit card. Furthermore I am receivning debt collecting emails and text messeges to make a payment! How can this nightmare end!! I have been a customer since 2005.