Telkom defaults on contract.

Had three contracts with Telkom because they were partnered with MTN. No problems there, because MTN is strong in our area. Since July 2019 Telkom dropped MTN and partnered with Vodacom. Now have NO SERVICE AT ALL . After frequent visits to Telkom branches, numerous letters asking for assistance/clarification and having a Telkom technician around to verify that there is no signal, I am still having to pay Telkom for a service which they cannot supply. Telkom say that I am breaking the contract, whereas it is they who have broken/defaulted on the contract by not giving me the service I am paying for. Anyone out there have any ideas how to resolve the matter??