Difference in Charged amount to Contract

I Purchased a Samsung tablet contract less than three months ago in the MTN deals book the 2gb contract was R 300 per month.<br> The first month I was charged extra, this was expected as there are always new connection fee's.<br> Then last month (my second month I was charged R 318.99 and when I complained at my dealer (Knowles) They said they would look into it so I let the debit order go, However I see once again the amount I am being charges is R 318.99 and when I went in to ask again I was told MTN had an increase, Now I wont complain about the R10.00 my cell phone contract increased by as I have had that for many many years However I refuse to pay the extra 18.99 per month for my tablet contract as I signed that contract less than three months ago, if I have to abide by my contract so does MTN for the 24 months.<br> <br> I WILL NOT pay this amount either MTN drops it back to R300.00 as per the contract for the full 24 months, I signed and my money over paid re-imbursed or I will happily return the tablet and the contract can be cancelled. I don't mind which I budgeted only for the R300.00 per month and will not pay more.