Bad Service

For the last couple of months I have been unemployed and was unable to pay my accounts (I know this is not African Banks fault it is mine), at about the middle of October I got a call from a lady from African Bank about my account. I told the lady that I am now employed again but I am not able to pay the full installment I am only able to pay R300.00, she then asked me if I will be paying via Debit order and I said to he no as my other account is frozen and I am using a new savings account I will pay either at the Bank or at one of the branches that they specify, she then said to me not a problem at all. The next day a guy phones me with the same story and I said to him exactly what I said to the lady the day before and he also said to me no problem. I then paid the R300.00 on the date that we agreed upon. Today I got a call from another lady that says my account will be handed over as I am not allowed to pay Cash as my contract is for Debit Order, I told her but how can you hand me over when I am keeping to my end of the agreement. She then told me its not her problem I never signed a form stating that I will now be paying cash. Why was I never told that I needed to sign a form.