I understand your dilemma. She’s someone you have a phone relationship with only — you’ve never met in real life. And the phone relationship is over work phone calls, on work lines. I think that when you do get to talk to her, you should flirt with her and try to draw out the conversation. If things go well, ask her if she’d like to talk on personal phone lines, and if she does, exchange numbers and pick up the conversation outside of work. 😉