WORST BILLING NIGHTMARE!

I spoke to an agent from NDS trying to find out my balance on my cell C account as I wanted to settle the it, this was on the 30/03/2015. the first time when NDS contact me for collection & I spoke to the lady called ketshepamang I was informed that I owed R8000' something & to date I paid them R5600. when I phoned NDS trying to get a correct balance cause I wanted to settle the account and I spoke to another agent telling them I'm not sure if I need to pay R2800 or R3200 to settle the account, they then advised that my balance brought forward is R4000' something, telling me that there is an additional collection fee of R900 charged to my name! This really got me mad because it was the first time I learned of the charge, when from the first time I was phoned for collection I was never informed of any additional charges. I phoned again on the 31 of march & spoke to Gordon who advised that I should wait before Involving lawyers, so he can first escalate to his manager for them to try retrieve and listen to my calls to hear if I was advised of the additional collections fee or not, to date I have not been contacted with any feedback, I mean it's the 9th of April & im still waiting!