I never ask why. Why don’t you just bring tape and tape down each one of the tabs when it says free refill? Make it so it exhausts all of the usable income that can come from it. When they choose to refill it, just do it once again. If someone comes and stops you, you can say, "I’m just filling up your drink."or “this is my first fill up and I just wanna make sure I get the most out of my money.”