PLEASE REINSTATE MY INITIAL CONTRACT AND PAY MY MONEY BACK!

In January this year I took two contracts for my sons and the total payment per month was R1735.86 and I was comfortable with this. Out of nowhere in June, some MTN service agent called one of my boys telling him how they can increase data allocation and also have the payment go down by R200, i.e. change from R900 to R700 on his contract. At first I wasn't for the idea because it didn't sound right but this agent persuaded me into doing it, promising to help me save R200 while my son receives more data than before. I asked him if he's sure of his story because it sounds too good to be true and he gave me his word. *To my surprise and disappointment and irritation, my new payment per month moved to R1945.34 as at 01 July*. Luckily for me, when I asked him to do the same for my youngest son's number (during our discussion), he said they can only do one number at a time, otherwise I would be sitting with R400 extra. ALL I ASK FOR, IS FOR MY SON'S CONTRACT TO BE TAKEN BACK TO WHAT IT WAS, AND THE EXTRA MONEY I WAS CHARGED BE CREDITED BACK TO MY ACCOUNT. Honestly, I'm not in the mood for fighting with useless pathetic ****s.