My wife and I had a similar experience at Sublime regarding the tip last December. The service was good and the dinner was very good. When the bill arrived I noticed the 15% service charge was added in,
so I increased it slightly to bring it up to our regular 20% gratuity. When the waiter arrived to take payment he actually said "Is that all you are adding for a tip"!! I said you have already added 15% to the bill to which he said that 15% is a government tax to which I said that there is no government tax on food and then the waiter said that he gets 5%. That experience left a very bad impression on me and we haven't been back since and have no desire to return.