Unfortunately one can only turn all the voices off or try to live with it. Personally I find the voices so irritating I can only play for ten minutes or so before quitting.
Recently I did a bit of a fix for the RAF ones, and replaced all the controller samples with silent files, mic clicks and ambient chatter etc. I also swapped the pilot voices for popular 3rd party ones. It made a big difference to how the game feels. I've been working on the Luftwaffe voices a bit, but it really needs a German speaker to make a proper go of it.
You can grab the latest version of the RAF ones here
http://forum.1cpublishing.eu/showthread.php?t=41355