Easy to open, harder to close!

We have requested to have our RCS card cancelled in November 2015 but we keep getting SMS notifications about settlement balance. At the time we, paid an amount of R109, which was supposedly the settlement amount, after we were told that we did not send a written request to close the account. After paying the amount, we submitted written request to have the account/card closed/cancelled but surprisingly this did not happen. We even have reference numbers to prove this but now we are told to pay R370, which keeps accumulating interest. I have written emails with no help! Had we known that this was going to lead to this kind of frustration, maybe we would not have app**** for the card in the first place.