Get filled into JG even when other people in the team are Queued up for JG?

How and why is this even possible? I suck at jungling... maybe i suck at every position but that's my worse one... yet I get filled into Jungle when even mid lane says that they queued up for it.

So i suck it the fuck up in Champ select cause I'm sure the last thing anyone wants to hear about in champ select... someone bitching about getting filled but hey.. guess what, I get fucked in JG cause XP is gutted and cant gank for shit.

so tell me why is it possible for someone to get filled in a position even when someone else is Queued up for that shit?