Bad service

had a bad service yesterday at checkers Northgate...

I paid with 200rands my change was R140, I was its 140 placed it inside my pocket when I got to the taxi later on only to find out that I was given a half of 20rand which I ddnt not notice we I was give I was in the middle of the R100 and the other R20

So today I went they checked the cameras I even asked guy thabo "Management " to take a video wot his phone to show me hence he says the R20 is full not half even when I tell him my side of the story

Now what will I do with this half R20 given at checkers Me and my colleagues we buy there each and everyday then am being treated like this