Telkom Direct

I had 10GB telkom contract, their sales person called me to offer me 20GB for R99, they said the old 10GB was gonna be cancel and be replaced with the new sim. Today they billed me for both sim cards. When I called, the lady told me it was not cancelled, they can not cancel a contract unless contract ended. I feel mislead and ****med. Its more frustrating that when I call them, they keep on giving me numbers to call, no body is resolving the issue. I m so upset!