Vodacom just want money but don't give service.

Been with Vodacom for 2 years before this incident. Long story short. After purchasing a contact with Vodacom and it coming up to renewal I decide that I would lower my contact seeing as I have a perfectly good working phone and just needed a sim contact. So I went into the Vodacom Glen store and spoke to the sales consultant. Once I was happy with my plan I confirmed with him that I was only going to pay x amount so there would be no hidden cost or no increases (this is what I will pay for the 24 months) . He rep**** yes you will only pay x amount a month that is it. So I said OK perfect and signed. 3 month go by and I have been paying the correct amount. On the 4th month I noticed a debit order going of for almost double the amount. So I went back to Vodacom and asked why. The consultant then turned to me and said no there is a bolt on and that I have to pay the amount of the contract. So I said but this was not what I agreed on in the first place and secondly why for the first 3 months was my debit orders x amount? This is selling under false pretences and is against the CPA. I then said I want to cancel due to the fact my trust has been broken with Vodacom and that this is not what I wanted. We then phoned the accounts department at Vodacom and was ridley told no I have to either pay the monthly installments or buy the contract out. So I refused to believe that I'll be financially held against my own will when I did not get the service and product I originally wanted and was sold under false pretences. Vodacom could not even say let's see what we can do to assist. They flat out just want your money and have no regard for customer service or satisfaction. Selling under false pretences is against the CPA. If someone from Vodacom HQ could help to resolve this matter it would be appreciated.