Wrong charges

I took a contract with Telkom mobile 2 years ago with no problem. Last December I went there to upgrade it, but to my surprise I was advised to pay R150 upfront to the contract. Now in January I just received an invoice which is way above the expected amount and when I ask no one can explain it. I spoke to Kgomotso from the call center were I asked her about hope I can get that t to be sorted and the only way is that I should go to the store or use the internet or else I'm *****ed. So I urge ppl to be on the look out of companies like this one because first ppl complained about the data, now that ppl are aware of data they rob us with the bills. I really regret upgrading I should have just cancel the contract I was not gonna see this mess at all.