Poor service

I perched a i pad last year November .I asked the agent for a top up wich he did not do .I phoned him twice and i communicated with him via e-mail about the top up and he ensured me that there is a limit on my account , just to find out that this was not true and now i'm sitting with a bill wich i refuse to pay seeing that non of this is not my fault .I phoned the call center for assistant regarding this matter and they could not help me , i phoned the head office,no help , i spoke to almost everyone that's working for Mtn but they just don't care !!! i really do regret taking out a contract with Mtn !! My first time ever i took out a contract and this is what i get !!!!!