You only have to change 3 parms if you configure the OBi manually.
Enter OBi expert configuration.
On the left column click the + sign next to Service Providers.
Click ITSP Profile (A, B, C or D) SIP
Change ProxyServer to:
callcentric.comClick SUBMIT on the bottom of page.
Wait for reboot
Click + next to Voice Services
Click (SP1, SP2, SP3 or SP4) Service
Change AuthUserName to: Your Callcentric Acct#
Change AuthPassword to: Your Callcentric PW
Click SUBMIT on the bottom of page.
Edit:
I forgot something.
If you are using SP2, SP3 or SP4:
Under Voice Services -> SPx Service
To the right of X_ServProvProfile uncheck OBiTalk Settings and Device default
Then select the corresponding profile (B, C or D)