Over charged by R100 and no slip

I went into little falls around mid day (just after lunch) and bought a pair of shoes for my 1 year old. Both my kids were a little noisy so i rushed out the store without checking for a slip. While checking through my card purchases via online banking I noticed a charge of R155 that day instead of what i remember between R51 and R55. All I have is the shoes and the bag and no way to prove that i was over charged - not by a few cents but by a lot and on top of that it is highly suspect that i got no slip. I keep all my slips to document how i spend my money to make sure i stay on budget - thats how i know i didnt just throw it away.