Final balance owing paid, but still getting calls

I was put on retirement with a 30 day notice in January 2023. I called MRP to obtain my final balance, which I then paid in full and requested to close my account. I also sent an Email in that regard. I am now harrased on a daily bases regarding an outstanding balance for Data charges for a Sim card I never used, but paid for. These charges were for the months after I had canceled everything and paid the final balance. Don't these people talk to one another or make a note on their system, after they called me. The service is shocking!!!!