Balance not corresponding to purchase made

I have an account with Mr Price, I had a balance of R487.51. On the 09th of June I made a purchase of R339.98 and then on the 10th I made another purchase of R225.98 all of a sudden my balance is R1,628.00 and it is suppose to be R1,083.42 Kindly advise as to how did it get to that amount. I called the call center and no one could explain it, today went to the store and still no one could explain it can you please fix this as it's really annoying I will not pay for something I don't know