Sportscene canal walk sale item scans original price

I went to sportscene in canal walk and bought a pair of kiddies old school vans that was on sale so I suppose to pay R400, when I got home I checked my slip and actually paid R700. I called the store and told them about the mistake they made and that the extra they charged me should be put back on my account. I was told that I have to go back in to the store and speak to the manager because I'll need to fill in forms.... Bare in mind that I live very far from canal walk. This is a huge inconvenience for me because I have to take the day off from work to do this. Who will compensate me for the petrol that I will need to drive out. With today's technology this is ridiculous!!! This is the stores problem, not mine.