non disclosure of extra costs

I had an upgrade on the 1st of November. Sales person was quick to sign me onto a new contract - no issues whatsoever. Does not however explain to me that I will be paying 2 contracts this first month. Being an ex Nashua customer, this should have been explained to me. Now I sit with a bill of R4000.00 which I cannot pay. Because people are too quick to make a sale, and miss out important details. I am now paying for my new contract and my old contract altogether in one month. Thanks MTN you're great. While you're at it why don't you take one of my kidneys too. Oh and a leg. Worst service ever. Calling the help line doesn't help either. If I do not get this matter resolved I will definitely be taking this further, as I was not notified that this would be occurring where I would be double charged. And I definitely will be looking into changing to a different network. I cannot keep a contract with a place that I feel I cannot trust with my money! Notify your customers of extra charges!! This is an amount I cannot afford to pay at this point in time. As I was not aware of the fact that I would be paying both the new and the old account in one God damned month. Assistance would be nice