CharlieNY - welcome to the forum.
This will use you GV service on sp1 to "fork" the call to your cell phone at the same time as the OBi phone is ringing:
Voice Services > SP3 Service > X_InboundCallRoute:
{ph,ph2,sp1(917xxxxxxx)}
Make 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.