Unfair treatment

On the 22nd of September 2017 I called in to settle and close my contract. We had an agreement that they will deduct the whole outstanding amount in order for them to cancel the contract. The debit order was scheduled for the 29th of September as per our conversation. I went on holiday under the impression that everything is in order. Today I received a call from their attorneys advising me that my account has been handed over. This is the second incident were I've been abused by the network. The first one I let go but this time I'm enough. I worked hard to sum up the amount to settle the account in order to rectify my credit record. I want to clear my name and they are hindering the process. This time I'm going to fight, I'm frustrated.