Vodacom mislead with direct marketing

Vodacom called me and told me I can reduce my costs for Data because I am a good customer. I received 2 simcards with packages marketing. When I received my statement I only discover that it is for a new contract for data which I don't want. I went to Vodacom shop, the lady tried to helped me to cancelled the 2 new contracts. After several calls and lastly the phone was cut off with no respond according to the one sales lady it was already more than 30days and I can not cancelled - but the vocacom saleslady at the store confirmed that it was not over 30 days. Please help me to cancel the contract I do not need the data