Unfair Default listing

I've been unfairly listed on the credit bureau as i was only notified by the debt collector only once and where i did not even hesitate to settle the account. As if that is not enough, Vodacom handed over my account to MBD Debt collectors who are so *********** when it comes to communicating right information to clients. First agent said i have to go to Vodacom store to settle the amount which i did, when i call to obtain settlement letter i'm now being told that i should've paid the amount into MBD account which I was never provided with when arranging for settlement. Ssecondly i was asked to send proof of payment to their email address and subject as 'proof of payment' and wait for a day before obtaining the letter. Calling the next day to obtain the letter, i'm now being told that i need to use my ID number as a subject. Calling a third agent, i'm now being told i need to use a reference number as a subject. All these have been done and none of the methods are materializing as today i still don't have a settlement letter and being Defaulted on the credit bureau.