The only thing I would like to add to this thread is that you should not trust anyone to tell you what the contract says....read it and interpret it yourself. I was burned a few months ago by trusting a captain on a scheduling issue.
On this particular day (last day of a 4 day trip), we were delayed on our first flight of the day into the hub because of low visibility at the outstation.... it was fluctuating between 500 and 1000 RVR, I believe we needed 1600 to takeoff at this particular airport. Eventually we got the 1/4 mile we needed and took off.
In any event, we were delayed 2 hours in getting to the hub, and we were going to be late for our scheduled flight to Mexico by about 90 minutes. The company doesn't like to take big delays on international flights, so we were hoping that it was recrewed so we could go home.
Sure enough, on the ACARS reply to our in range report, we get HOTEL/TERM for all 3 crewmembers (It will tell you your next flight number and gate assignment if you're supposed to work another flight). The captain said we had lucked out, and I was pretty happy since I had plans for my days off anyway. We land, and I hop on my flight to commute home. I turn my cellphone off when I board the plane.
When I get home, I turn my phone on, and crew scheduling has 3 messages on my phone asking where I am, and that they were expecting me for the Mexico flight.
Turns out, somewhere buried in the contract is a clause that says if your schedule is modified in any way as a lineholder, you are required to call crew scheduling to verify the change...this almost never happens realistically, since crew scheduling is usually swamped with calls during wx events....you will be on hold for at least 30 mins if you attempt to call scheduling in these situations...you always just go where ACARS tells you to, and verify with the gate agent if it tells you to work another flight. Oddly enough, this is actually not a requirement for reserve pilots....if there is nothing on your schedule 15 minutes after block in, you can just go home without calling.
Well I got burned on that one, the chiefs didn't care that ACARS was inaccurate, nor did they care that crew scheduling admitted that they had "recrewed the flight at one point, but changed their mind". They put a missed trip on me....moral of the story....err on the side of caution, go ahead and call crew scheduling if you have a question about your schedule, because there will be no mercy if they think you're trying to take advantage. It's not doing anyone a favor, it's looking out for your own hide. Turns out they got ahold of my captain somehow and he ended up working that Mexico flight. I have no idea if what he told crew scheduling or the chiefs in some way hurt my case, but it sucks either way.
This "screw the company" mentality can end up screwing YOU if you take it too far.