Wanted to let everyone know that there's a guide to help us set up call features with Star Codes.
For example:
*69 Call Return
*60 Call Forward on Busy (Enter Number + #)
*61 Disable Call Forward in Busy
http://www.obihai.com/docs/OBiDeviceAdminGuide.pdf (http://www.obihai.com/docs/OBiDeviceAdminGuide.pdf)
Hope this helps!