Breach of contract & poor service

Vodacom offered to convert my SMS bundle to talk-time minutes, at no extra cost. Two separate consultants contacted me to offer me the service, conversations recorded, and I accepted the amendment. Only to find that I’ve been billed R200 extra last month! I contacted Vodacom 2 weeks ago & they assured me that the issue will be resolved, but I have been billed the additional amount yet again for January. This is completely unacceptable & it’s a breach of contract!