Double payment on Homeloan, refund refused

Last month I contacted the Homeloan division and informed them that I will be making a cash payment for my home loan therefore they should cancel the debit order from my account. The lady I spoke to suggested that I should send my request in writing, which I did. <br> <br> I called the next day to check on progress and I was told I will receive an sms and an email notification. I did received both and my request was approved. On the 2nd of November, I was shocked to see that an X amount for the Home loan has been deducted from my account. Though a cash payment was made a week before the deduction yet they still went ahead, ignored my request, my earlier full payment and still deducted from my account. When I called in requesting for my cash payment I was told to write a letter of request, what kind of bull **** is that?<br>