Holding my credit report hostage

Standard bank is holding me hostage with my credit report. I have phoned out over 3000 rand of airtime to try and resolve this issue Every time I phone them they do not have any accounts on my name ! but I'm flagged at the credit agencies because of them , When you phone they put you through all over and you have to answer all there security questions just so that they can put you through to someone else. So how can I get a letter stating just that from a bank that can not help you to clear my name. I have been struggling since last year. I can not even rent a house because of this. All I need from them is to state in a simple letter that I do not have any accounts with them that they can see or had .... THIS IS NOT POSSIBLE FOR THEM Standard bank is making my life miserable