Non existing service

I used Mweb Africa as an Internet provider in 2019. I cancelled with them because we were more off than on the Net. They have been deducting my subscription off my Credit card since then. Well over a year now. I have spent hours on their call center with agents promising me that the problem will be sorted. When you try and call their Head office direct you just don't get through even when they thank you for holding. I am at my wits end They owe me about R5000.00 in refunds for a service I did not use. How do I get to talk to someone that can assist me. Deon Joubert 39 Stinkhout Crescent SE3. Vanderbijlpark ***