Interesting point, though.
If I am trying to arrange a meet with a WG for the first time, I try calling initially and, if no response, (usually the case) I then send a text along the lines of "Hi, just tried calling but got no reply. Are you available . . . ." If there is still no reply after an hour or two I send an AW email (not booking request) saying " Hi, I tried calling and texting you earlier. I would like to make a booking. Are you available . . . ." If there is no reply within a reasonable time or the email remains unopened then it is on to plan B.