Make it impossible to settle account

Received a settlement letter for my Wife's personal loan, the reference number stated in the letter is invalid when paying via Standard Bank EFT. Contacted them and get told there is a special reference number when paying from Standard Bank, get given that reference number only to find out that is also invalid. Now told the only way to settle is to go to the bank which is ridiculous in this day of technology. It seems that they are happy to just keep taking the monthly minimum payment and do not want people to settle accounts.