I should get what I pay for

I've encountered this problem ever since I arrived in cape town last year December, never anywhere else in any provinces I've lived in before. Whenever I buy or eat at any restaurant or takeaway restaurant I'm expecting to get what I pay for. For example,If I don't eat garlic and I ask that it be taken out of my meal I don't see why it should be a problem. But at chicken licken at 14 viking way, salberau, the only one near me, I'm forced to eat chicken breast when I don't even eat them at home or anywhere else. Whenever I ask for specific portions I'm told I'm not allowed to choose. How, when I'm the one paying? I'd appreciate the feedback so I can understand how or why are we being forced to buy stuff we don't eat?