Horrible Customer Service

My Debit-Order is Scheduled to strike on the last day of the month, in Feb this meant the 28th. The D/O went of a few hours before my salary was paid, resulting in failed D/O. I went to a Vodashop within the next two days, to make urgent payment and prevent a bad record. The lady advised that all was fine and my account was not in arrears, she told me that due to everything being fine, I could not make payment, even after I assured her my D/O had failed. Two days later, I was notified that a loan had been turned down due to a bad vodacom record - the bank requsted a letter from Vodacom stating I was not in arrears. I went to the Vodacom again, made full payment (this time they accepted), but they REFUSED to provide me with a letter saying that I was not in arrears. I was told to call a number, in which I explained everything, but they would not provide such a letter, even though they admit I am no longer in arrears. I asked to speak to a supervisor, who was busy. I said I would wait, but was quickly informed that the supervisor was actually \knocking off". How can they blatantly REFUSE to provide me with a letter stating I that I am not in arrears"