You can also edit the teams to change the members, or limit it to a single or two characters. I was surprised to see you can even change which class they are:
http://www.youtube.com/watch?v=pgVGw5AKlX4
It's not going to sell you on the game if you hate them all, but it might be fun to mess with once you're bored of the game.
As for the voices, I've never substantiated it since I've never owned the PC version, but someone said once that in the config files there was an option amusingly labeled "charmy_shutup" or some variant of that that muted the constant chattering. Could've been bullshit, I never got to look for myself.