MTN is a *******

I had a contract with MTN & I closed last year around December, when I closed it I asked the assistant that was helping me through out the process if I don't owe any amount she said no amount will be owed and the account was closed. Then I recently app**** for a loan at one of the banks and they couldn't grant me the loan cause MTN had handed me over to credit bureau and I've went back to contact MTN and I even settled the amount that is due but now they don't want to give me a paid up later to submit to the bureau to clear my name yet again at the bureau the assistant told me that is was a wrongful hand over by MTN and it mandatory for them to give me a payed up letter but when I contact them they say I must wait 21days but the amount that I payed to them they say it reflecting but they don't want to give me my payed up letter.