That 12.5% service charge is a tip (you don't have to pay it if you don't want to, and it will generally go to the servers).
How can you refuse to pay? It's part of the bill, isn't it? In most restaurants I've been so far at least. Also foreigner, so maybe I am missing something.
You can say you don’t want to or state some other total you’re going to pay that’s >= to the rest of the bill. Obviously that’s awkward and that’s why they make it the default, but you can pay less/no service charge/tip if you want to.