Pathetic service from african bank

I have a personal loan with african bank. I specifically gave them the instructions to debit my account on the 28 of each month. No one in this bank ever listens!!!! For the past 5 months they debit my account on the 22/23/24. What ever funds are left in my account before pay day they debit it. Whenever money is transferred into my account from? Savings, they debit it. Irrespective what day of the damn month it is!!! NO one ever answers the calls. The phone rings forever. No one returns any damn calls. I'm sick and tired of the pathetic service from this useless ban****!!!