R2 donation taken without my consent

I purchased streetwise 3 at kfc adderley parade today and I used cash as a method of payment. The cashier was Siphokhazi she asked me if I wanted to donate R2 and I said no because I don't have but she took advantage of the fact that I have change and deducted the whole R8 .My question to KFC is that are you forced to donate? And how many people have you done this to ? Because if I didn't check my receipt it means I wasn't gonna know.the only disadvantage is that I checked when I was at home .I need my R8 back because I never agreed to donate to anyone