Overcharged for phone protector and pouch

On Saturday 02 Feb 2019 I bought a cellphone screen protector (selling R199) and a pouch selling for (R250) and I was told to give cash while they have a speedpoint I had no cash since I wanted to swipe for it. Eventually the guy agreed to use the speedpoint, my mistake was to proceed with the transaction without looking at the amount he punched on the speedpoint. I realised that he punched R699 for the 2 items and I was already far from the complex. I would like to get help to recover my money, which for me is that these people are used to **** or overcharge customers like me who believe that they are honest and genuine. Imagine the 2 items doesn't come to that amount charged and again the protector and pounch doesn't cost the amount he told me they are worth, that's way too much to pay for.