Non-existent call center assistance

ONE STAR IS TOO MANY FOR THIS COMPANY! My LTE device stopped working three weeks ago. I spent many hours on calls to the call center. I took the device to a store. Long and short is that it seems Telkom does not have coverage in my area for LTE anymore. They closed the call twice without solving the issue. I have now paid for a full month almost without having the service that I pay for and they said in so many words that I will keep paying until the the contract is finished even though Telkom is at breach of contract here and not myself as they cannot supply the service that I pay for on the contract. They refuse to cancel it without doing an investigation but they keep closing the investigation without resolving the issue. Where does one go from here?