If the ban is for a single channel/room, rather than the network, here are a few possibilties for you to try.
1) If the network has chanserv capabilities, type /msg chanserv info <channel name> and note who the founder is.
Once you have the founder's nick, you can try pming (/msg) them, or if they aren't online and memoserv is available, try sending them a message via memoserv. For more info on sending a message via memoserv use /msg memoserv help
2) Join the local help channel (#help) and ask there for assistance. While most networks state that sysops (IRCops) won't get involved in room bans, quite often they will listen and try to resolve the situation.
If this is a network ban, then try accessing the networks webpage.
I make no promises or guarantees that any of these will help.
