Deal with Jangl?

Jangl.com (in beta) has gotten a lot of attention and even made it to the 2007 Connected Innovators. But I don’t get this service. I signed up, my sister in the UK signed up. I got a number for her and she got a number for me. We both set our preferences to go to Phone. However, everytime I call the number I got for her email address, it goes directly to voicemail. Same for her.

I have been trying to figure out what am I doing wrong, checked out their support pages and everything. The idea is for people to not have to disclose their phone numbers, but shouldn’t they at least connect as the website claims they can?