Vodacom ********

I bought a phone in February I called Vodacom the beginning in march and asked them to put a limit on my phone cause it was an open contract and because I'm saving to study next year that's is why I asked for a limit on my phone. The sales consultant I spoke to never put the limit on and for some reason my phone account for March was R5286.27 after asking them to put a limit on the account. I agreed to pay the R5286.27 and took the contract sim out of my phone to first pay that R5286.27 up and then maybe use it again .The other lady I spoke to at Vodacom then blocked my whole account even the ussd code and I couldn't do anything with the card which was not a problem cause I was happy that I can pay the R5286.27 off. All of a sudden I got a statement yesterday from Vodacom saying my account for April is R4619.63 even when I did not use the account for April. So everything on my account is blocked but I get a bill of R4619.63 so my total Vodacom account is R9906.00 that I must pay can anyone please advise me as to what can I do to take this matter further Vodacom is ripping me off is it because I'm young and they think I'm stupid or what I am very disappointed in them