No slip no change

I made lay-bye n lost my slip went back to pay n they asked for my ID n they gladly helped me...now some of the clothes are too small I went back to make exchange and they told me I have to present them wth my slip of which I told them I had lost...now they refuse to help me they kept telling me that they can't gv me change n I have no right to getting a change of myyy money....i asked for their head office numbers n they told me I'm gng to get the same response from them...pls help Its either they gv me wat I want or I HV them their clothes n they gv me my R960 back