Account Settled but Vodacom re-opened it

I had a cellphone account with Vocadom which was being handled by VVM collections department, i paid the account and closed it October 2014, now they came back and say from April 2015 they picked up an error from the system and that i still owe them R3110, while i paid the R8 600 i was requested to pay in order to close the account. i have now taken them to the lawyers to have this matter resolved, they will close that account i will see to it. I will keep writing in this forum until they clear my name, i will not pay and amount that i do not know never