Problem with a quest

[Stateofwtf]

I was in a group and we completed a quest. The others got credit for it but i didnt. I accepted the quest prior to doing it and i was not on any lockout timer. I asked one person in my group and he said talk to a gm about it. So i typed ]gm ingame and none was online. How do i talk to a gm?

[Stateofwtf]

Also I have screen capture of me not getting credit. I dont know if that will do me any good but, Im just doing what my group mate suggested and contact a gm.