Large Incorrect Amount Debited off my account

I am very dissapointed with the service i get from ABSA, every month and its the 3rd time now they deduct R2900 from my account for a person loan i took with them. I communicated this with them last month and asked them to refund bank a difference of R1400 back to my account and every month i must make a call to rectify this and it inconveniences me. I have a loan with them, savings and my salary gets paid on their account every month and this is what i get for being a client??? someone please sort this out!!!!