Paid up letter

I paid up my account end of September, im still waiting for my paid up letter, I have called in every week, to 3 different departments, because each department blames the other, finally requested to speak to a manager, was given a number ***, got to a receptionist who transferred my call back to the customer service who gave me that number to begin with. While all of this is going on, im still getting calls being harrassed by the company i was owing saying my account is not settled, the only way they will stop calling if i send them a settlement letter, which im struggling to get from MBD. Honestly the worst service