Poor service and false advertising

Recently a call company on behalf of Vodacom are calling customers. They asked me if I would like to convert my contract SMS bundle to either data or airtime as I am not using it - for a minimal extra amount. Then almost 5 times more money (to what was agreed on) was subtracted from my account later on. I called Vodacom and they really helped me, will change my contract back to its original state and do an investigation as it was in my opinion false advertising. HOWEVER, the company is still calling me daily and the more I explain that please I have been offered this product, they say "okay its fine, goodbye" but call me back again the next day. Very very poor service and a system that is not working.