Additional charge that I was unaware of.

I had a Uncapped Wireless Broadband contract for R799 each month which included 100GB of data and 50GB utorrent data. We then saw the plan for R369 p/m which we thought included 80GB of data and then downgraded our plan to that. They then said to downgrade it will cost a monthly fee of R133 in additon for 1 year. So anyway, we went ahead. We then realized the deal was only 40GB day and 40GB night which then turned out to be way too little and decided to upgrade back to the R799 Uncapped deal. When asking if there will be a charge to upgrade, the agent said no as we will take out a new contract. We then completed all and when receiving my statement saw an amount of R901.57 added to my account for the previous contract. This was not discussed with me and I don't think it is fair that this is billed to me. Had I known it was going to cost me almost R1000 to upgrade, I would never have done so. Please can this be queried with your accounts department and reversed as I was not aware of this fee.