MBD is robbing me

My identity clothing account was handed over to MBD because it was in arrears. So I took a decision to get help from my union, they normally help pay off workers debt whenever they fail. They than asked me to provide them with settlement statements of all my debts.

On the 30th of May I phoned MBD asking for a settlement statement they sent it on the 8th than on the 9th a full amount of what was written on the statement. Than on the 30th of June they sent me an sms that I have not honored the agreement I made of R787, 95, I phoned them and explained that I have paid all that I owe them, they said the person that drafted the email made a mistake so I must pay the money.

I feel cheated seriously and on top of it all they say they are sure I made the arrangement God knows I never did as far as I know I do not owe them anything now I'm going to be blacklisted and that will be the end of my dream business because I need a loan for my small business now they are doing this to me after all my efforts trying to keep my credit record clean

Please assist me I really do not know what to do