Where does it say that?  I checked my manuals and contract but did not see it anywhere.  It is a courtesy that you/we may provide but it is not my job to walk around with an "answers here" sign.  If somebody wants to ask a question they can and I will surely go out of my way to help but it is not my job, that is the job of those people that "work" the airport info booths but they are usually volunteers.  
If I need to make a phone call during a turn, you can believe I'm not going to go run to a corner so a passenger does not see me talking on my phone.  I'm not on the clock when I'm in the terminal anyway, so why can't I use my phone?  I'm paid block in to block out.  That being said, no I don't own one of those things and I will try to help out whenever possible but come on...
I think there are plenty of unprofessional things pilots do and we all look bad because of it (no hats, wrinkled or dirty uni's, etc.) but I don't think this is one of them.