Microsoft Office 365 Audio Conferencing Extended Dial Out for US and Canada is an add-on license that offers “virtually unlimited” calling minutes for North American users. Although subject to a fair use policy, users with this add-on won’t deduct capacity from their organisation’s pool or Communication Credits.
The license is available via EA/EAS, EES, CSP, and via the web for commercial, Edu, Non-profit and US GCC customers. I haven’t seen pricing info yet but you can see a little more info from Microsoft here.
Cloudy with a chance of Licensing 