The auto attendant has its own setting for Primary Line. Assuming that GV is configured on sp1 then the following settings should work for you:
Physical Interfaces > PHONE Port > PrimaryLine: SP1 Service
Voice Service > Auto Attendant > PrimaryLine: SP1 Service
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. Then move on to another page if required.