I have a data contract with Telkom for which I'm unable to use the data

I have a data contract with Telkom for which I'm unable to use the data. When I call them they say it might be a coverage issue. To this day it has not been fixed. I've been given Several case numbers and still no resolution. They keep deducting their premiums without calling to check if it's working. My latest case number is ***9. I would like to cancel this contract and be fully refunded.