price of items differs from shelve price

I have being to checkers hyper this morning (28/05/2015) to buy my son that is turning one a present for his birthday.. we decided to buy a ride-on toy.. we saw one (pop & roll) at the baby section that was on special for R399, we then bought that ride-on toy.. when I got home I saw the sms from the bank that the total of the purchase was R517,that is with two 500ml cooldrinks. I then checked the slip, and saw that I was charged R499 for that ride-on toy... I feel a bit frustrated about this.. as it will cost me R100 petrol and R18 toll fees to go back there for a return.. I feel that checkers must reimburse me for their mistake, as it will cost me more if I must go back to return the item.. also feel that this is very unproffesional.