Billing paid up account

Since my account was handed over to their attorneys MBD now for over a year I've had to put up with their rude call centre agents who abuses the power of being a collector but finally paid up the account in October 2017 and immediatelly called in to request for a paid up letter which even today i've not received.After 3 months of being transferred from 1 department(call centre)to another today I finally spoke to the attorney Arthi Singh who couldn't understand why am frustrated because apparently there is an outstanding balance on this account which I failed to understand of what when my account was fully settled by myself in October, she rudely informed me that she's not handling this account she once again referred me to someone else who is handling this portfolio!! Meantime am listed by Woolworths as slow payer whereas this could've been all cleared up had they given me the paid up letter when i settled the account, went in store all the consultant could say was unfortunately he can not assist me as my account was handed over, what on earth do I need to do!!!!