No one follows up in this organization

Standard Bank incorrectly billed and handed my account over to MBD, after numerous follow ups Standard Bank rectified their error, reversed all the outstanding amounts and further closed the account. I am now stuck with a different contact centre agent calling me everyday to follow up on payment despite me explaining myself over and over again. The most annoying part of all this is, the same MBD keep sending me text messages thanking me for payment and settling the same account that I receive these annoy calls for. This only suggests that management has no clue what they doing and the contact agents are not skilled enough to escalate and follow up on queries independently. All I ask is that these people clear my name and stop calling me!!!