Downloading world of warcraft the burning crusade?

well i was playing wow. i was at kalimador so i took a ride on one of those birds and ended up on a island i never been in. once i landed there i noticed that something was downloading so i logged out. then i went to the menu and saw the downloading bar. i was downloading burning crusade. i don't know how this happen. i don't want to download it. i tryed to disconnect the internet but it doesn't stop the process. can anyone help me stop the downloading?