Over billing

On the 24th June 2015 I contacted Vodacom regarding my contracts I have with them for 3 phones receiving airtime monthly. I asks to have 1 of the SIM cards to be stopped from receiving airtime terminating its contract. Then asked for the other 2 SIM cards to change from R70.00 to R110.<br> In July an agent contacted me advertising a tablet, I showed interest and asked for it with a new SIM. Upon delivery there was just the tablet and no SIM card with it. I rejected the delivery, didn't even sign for it and the courier left with it. <br> Today I receive the invoice to my surprise the very SIM card number in June I requested to have its contract terminated and was confirmed terminated by the agent is still open and on top of that they keep ribbing me off