I had a similar conversation with a professor about a month ago and I was also nervous about it. I'm not good at talking on the phone (and never have been - as a kid I would run away from the phone rather than take a call, no joke), but it actually went really well. The first few minutes were kind of awkward, and you should be prepared for that (exchanging pleasantries, etc is going to be semi awkward with someone you've never met), but don't worry - we ended up speaking for over an hour and after the first few minutes it was totally comfortable. The professor asked me questions about how I got interested in the region I'm studying, my language prep, previous research and travel experiences, etc and that led to a conversation about how she got interested in the region. She gave me some really valuable insights about how the admissions process works at her school, and what kinds of things I should highlight in my statement of purpose. I had some questions written up on a post-it note beforehand (i.e. how big are classes? how many grad students study the region? etc...definitely nothing earth-shattering). We talked about funding as well, and by the end she said she would advocate for full funding for me with committee. All in all, I was worried about it, but by the time I hung up I was actually much more at ease with the whole admissions process. Not sure if any of this is helpful, but good luck! And remember, history professors aren't public relations execs or politicians...they probably get the being shy thing.