HIGH BILLING BY TELKOM

I did a contract with Telkom then in February I saw my billing was high. I went to their offices about this high billing and they said they fixed it then in March my billing was even more higher than in February I asked them what is going on and I spoke to one of their employees and I told them I'm not going to pay for extra money I don't know what is it for now they didn't get money on the March they are charging me payment rejection fee of R202.70 which I've never been told about it what suprise me more they are even charging me late payment interest of R11.73. TELKOM IS **** I've never heard of this and we as consumer we have rights what are these amounts for. Its the 4th of May today already the account has 2 interest.