I set up my Obi 202 with the Obi bluetooth adapter, and received calls from my Sprint mobile, but when I dialed **8 and a number, an outgoing called was not initiated.
The problem turned out to be the Google Voice enabled on my Sprint phone, that would ask me on each outbound call whether to use or not use Google Voice to complete the call. When the Obi initiated the call, this menu would pop up on the unattended phone, and the process would stop there.
I went to the Google 'Voice' app settings, and chose to always not use Google Voice (therefore use the Sprint number - I could have chosen to always use Google Voice) and once a default was selected, the process of initiating a call via **8 worked fine.