African bank says "we are you". I beg to differ!

It was a mistake opening an account with African bank and I only did it to build a credit record. The process from the start was a difficult one and I was afraid I was going to regret it and right I was. The problem I am experiencing now is that banks have to comply with a debicheck mandate. This is when a message is sent to the account holder to approve the creditors debit order instruction. African bank call centre has the responsibility of calling all who have not yet accepted the mandate. With that I am happy to comply as I owe them money and I pay my account on time with a debit order payment. My problem is that I have changed bank accounts earlier this year and even though this has been updated and African bank gets their money, they are still calling me as I did not accept the mandate. To date I have not received the SMS mandate. After countless calls from the call centre and instructions to visit my bank and call my bank in order for my bank to allow the mandate to come through on my account, I still have not received this sms mandate. The issue is according to one of the agents, that the debit check system sees my old banking details and sends the mandate there. Now unfortunately for me the consultant only discovered this after the umpteenth call. At this point I am severly frustated that this process cannot be resolved internally by African bank and that I am been harrassed daily regarding this. Whats more frustrating is that people call as if its a collections call and make no effort to read their notes. I have left many messages and explained this many times to consultants but nothing seems to be done. Everyone that calls seems to act as this is news to them. I was assured by a lady manager that this will be escalated and fixed and that I will no longer be harrassed. This was 3 days ago and I am still beign harrassed. I apologize for been abrupt with the consultants as they are just doing what they know but this process is not working and someone needs to think a little further and do something about this. I will definitely not be doing any business with African bank in future as this is more grief than it is worth. they start calling before 8 am in the morning and still call way after 6pm. I cannot deal with another person calling me to complete a mandate or make an arrangement to pay my account on a debit order system that is already taking payment correctly. I am a patient person but this is enough. Promises to resolve this have not been kept. Promises to stop bothering me for two weeks have not been kept. If i do not keep my promise to pay you I bet you will not be this lenient. THIS HAS TO STOP TODAY!