Assuming that GV is on sp1, then you need change from:
Voice Services > SP1 Service > X_InboundCallRoute: ph
To this:
Voice Service - > SP1 Service -> X_InboundCallRoute:
{ph,pp(ob290123456)}
where 290123456 is your OBiTALK softphone number.
Make the changes via the OBi Expert Configuration pages. From your OBi Dashboard, click on your OBi number and follow the prompts to get there. To change a value uncheck both boxes to the right of the value and leave them unchecked. After changing the values on one page, press submit at the bottom of the page and wait a few minutes for the OBi to reboot.
Your 3CX phone can have several accounts. Set one account as follows:
Account Name: Anything
Caller ID : Anything
Extension: 290123456
ID: 290123456
Password: leave blank
I am in the office – local ip: 127.0.0.1
Use Outbound Proxy server: 127.0.0.1
Of course, you also need to have OBiAPP running on your PC. I guess you know that as you can make outgoing calls