The phone must support SIP. If it is SCCP only, it will not work.
If SIP compatible, check the setup menu for the following settings (per OBi instructions):
EXT 1/Proxy = (500111345.pnn.obihai.com:5061)
EXT 1/User ID = (1001)
Ext 1/Password = (AnyPhonePassword)
EXT 1/Register Expires = (60)
EXT 1/Register = (yes)
SIP/Send Resp To Src Port = (yes)
This is all that is required to connect to the OBi.
Most of these phones have built-in phone books, call lists, redial, hold etc. .
Dial Map totally optional. Everything else should use default. Do a full reset before starting.