Telkom Incompetence

I have a situation where I had a contract with Telkom and they had to close my account and hand me over to MCS attorneys, which I delt with, by having a payment plan and eventually paying off the 5k dept left and thereafter I received a payed up letter in that year. This year I'm handed over again to P&p attorneys by Telkom for a 15k debt, which I understood to be closed when I was dealing with MCS attorneys.

I've shown them the paid up letter but they refused it saying it needs to come from Telkom and that they can't accept it coz apparently there was a payment missed at some point, which to me didn't make sense coz they talking about something that happened before I even cleared the initial amount with MCS attorney.

MCS advised I ignore them as they handled the account and we closed it but I don't wana be blacklisted without me knowing and refuse to pay for something suspicious like this esp after such a long time. But then now I get a sms saying Telkom has blacklisted me