The Collecting Agents

I run in a problem with my account, so they decided to hand me over what is there right to do so my problem now is the collecting agent is harassing me by the sense of the account is been paid they tell me I lie it is not showing I told them the amount that has been paid now they phone me 5 times a day telling me I made a arrangement to pay the amount what I told them I pay last month I told them I did not make any arrangement I inform you the amount I pay by the 12/13 of the next month they phone again we did not receive any payment on this account as yet so what happened with the amount I pay last month yes we got that but nothing for the new month what date is it today 12/13 so I ask everyone pay there account the end of the month is it not so yes but when will you pay your account on the other hand I ask what is my balance on this account sir after the last payment we received last month your balance stand at R900 but my slip show I only own them R200 so I ask where do you get R900 from I want statements sorry sir that you have to ask Stuttafords, Stuttafords sorry your account has been handed over who can I get my right balance?