I can't play dungeons

Im a brand new lvl 20 monk (healer/fighter).

I queue up fora dungeon, I find a team, I get into the team, everyone gets ready, and when is loading for the dungeon, as soon as this loading complets I get REloaded into the normal world droping me exactly where I was before the first loading screen, happens to me every time.

At the beneffits bar I get a litle square that says 30secs prep for dungeon and when this finishes nothing happens.

What can i do ??

PS: how much time do I have to play in normal wow to be able to play the classic version (I want to play hardcore realy bad)

PS2: I havent paid my first monthly suscription yet

Thanks for answers!! :)