Sorry it took me so long to get back to you! I know what you mean, sometimes it's much easier when you don't actually have to see their facial expressions when you're talking.
It takes some getting used to, but talking to them in person is a great way to get them to know who you are. Most people at my job find it funny that I consider myself a "closet introvert" because my job requires me to be quick and talk to people at all levels. Outgoing and just talking to people is not a natural tendency for me, I would prefer to sit back, take time to process, but I had to learn how to get out there. It makes me tired at the end of the day though. If you have a few friends try practicing and pretending they are company big-wigs. Another thing is to try to imagine it being just a casual conversation. If you stumble it's OK. I know a lot of company execs who are just as nervous as we are. :-)