telkom bad service

Telkom sales agent who offered me a data simcard since my contract is coming to an end...now I am being billed for the old contract as well as the new simcards and that's not what the agent sold to me because I specifically asked him what I would be paying for at the end of the mopnth, he said I'd only pay for the new data simcard that would be R99. I've been calling Telkom call center all morning and being sent from pillar to post, no one can assist me. I would like to continue with my old contract until it ends, Telkom.