I had a gate agent telling me that the flight was closed because it was a "quick turn and the flight needed to leave." Dec. 22nd 8 p.m. after a three hour delay because of a late aircraft with about 5 stand-bys waiting to get on. I was not happy and I asked her if she spoke to the captain about taking me as a jumpseater. She said she spoke to ops and the flight was weight restricted so no one else could get on. I told her I wanted to talk to the captain and she said the flight was leaving. I was sitting there watching the rampers continue to load bags, the flight was obviously not leaving anytime soon. So apparently a ramper overheard and went and talked to the captain for me and the captain had a talk with the gate agent and got me and two other people on board to get home for christmas. Thanks so much to that Mesa captain as well IAD-DTW.