Problems with monthly debitorder.

I've been struggling with my debitorder from last year December. I had to follow-up on my debitorder each month because my debitorder does not go of on the 25th of each month as I requested. I've been phoning Mtn customer service monthly asking the accounts department to set this right. Each month they tell me the problem has been rectify. I ended up with a phone being suspended each month because I did not have funds in my account for the debitorder Mtn set on the 17th of each month and not the 25th as I requested. I only get my salary on the 20th of each month. That's why I set all my debitorder for the 25th of each month. Mtn is giving me a bad credit record and I'm very disappointed in their service. I've been a customer for over 10 years and not once had problems with a debitorder. I will not continue my contract with Mtn when it's ended. It's sad to see how a network that once was very pleasant to use turned into a frustration each month.