Bad customer service

On the 28th May I paid R1780 by the branch which is the settlement amount now I get irritated as in everyday I get calls from African Bank telling me that I owe them roughly 4x call in a day it really irritates that means clearly someone is not doing his job that I even got the paid up letter but still calls everyday even 4x per day please clear this matter and call me with a solid solution I even called them to close it but it was not fulfilled I'm soo ****ed off especially regarding 4x calls per day how come did they send me the paid up letter but it was not closed as I asked them and again while paying why was I not offered vouchers like other customers they do get vouchers as it's also unfair....I really need clarity on that..