I believe that you could benefit from some general reading about what Google Voice, the service is, and how to use it. I could write a long, detailed article here to attempt to give you that level of understanding, but Google has already done that work; it's the Google Voice help center, located here:
https://support.google.com/voice/#topic=1707989The help center is divided up into nice, small chunks of information.
Google Voice is an inbound telephone call forwarding and message management system, not just a direct Voice over IP home/business telephone service, like Vonage, Callcentric, Anveo, etc. GV is designed to use one inbound phone number, which then forwards to up to six destinations, one of which can be Google Chat, which is what OBi devices use.
There are three ways to put an inbound GV number on an account:
- Get a new number from Google's inventory of numbers (first one's free).
- Port in an existing US-based mobile or traditional landline phone number you currently use with another carrier.
- Use a special feature available only to Sprint customers, which uses your Sprint-owned number as both your Sprint mobile and GV number.
If you want to get a new number from Google, you must also prove that you have some other, existing, working mobile or traditional landline telephone number in service. The reason for this is to attempt to control fraud and abuse by people who are taking advantage of the free numbers for robocalling, telemarketing, scams, bill collecting, etc. By proving that you have a legitimate, working phone number that you will use as your forwarding phone, Google can try to block users from grabbing multiple GV numbers.
If you want to port in your existing mobile phone number, you can do that for a $20 fee.