10% Service charge added to bill

I went to the Gateway branch on Saturday ordered two lunch time specials of prawns and a whole baby chicken. the prawns and the chicken had extra salt a over-powering lemon flavour. the coconut rice had no coconut flavour. my entire family were disappointed. To top it all off, there is a new rule that the 10 % service charge is added to your bill and has to be paid for . This rule was implemented a month back. I called to speak to the Manager who was also our waiter, I doubt he was the Manager and he said we had to pay. Service was pathetic , wont be going back.