Account of deceased user not being canceled.

My father passed away in Dec 2024. We handed in the paperwork in Jan 2025 to notify them. It is now March 2026 and the account is still active and the amount just keeps going up. They just say somebody has to pay. All queries just get ignored or just pay the account and we will close it. Their area managing blatantly insulted my mom when she spoke to her. How pathetic can you get?!