Cancelation refuse buy Telkom.

I want to cancelled my mobile Service with Telkom. on the 7 the June, of a contract that is more the 24 months old. Telkom refuse to cancelled my service and add a new contract without my approval to my account. I am not the only person that have this problem. Telkom service is the worst I ever use. Clarens do not have Telkom coverage. Way would I continue with Telkom.