If you've been given an assignment, you are not obliged to answer the phone 4 hours prior to the showtime. If they call you during that time, do not answer. Check sched+ to see what they're wanting you for. If they've removed the assignment and it suits you, call them and go home. If you're near the airport, try and duty in, then call them when it won't let you, and say I'm at the crewroom and I'm trying to duty in, do it for me please. "oh well we gave that assignment to someone else, you can go home". Great, show me dutied in and duty me out a minute later and I'll be going home if you don't have anything else for me. At least get the min credit for the day, it may count later in the month. If you call them before that, you ain't getting squat.