You're not understanding the basic concept of VoIP: The physical telephone sitting on your desk is not the source of your telephone service. It's useless without some form of telephone service. It is merely a "client", which is signing into a VoIP server. You are using the telephone service provided by an Internet Telephone Service Provider (ITSP). There are many ITSPs that simply offer telephone service, which can be "provisioned" or set up on a wide variety of clients (IP phones, ATAs, or software clients).
Google Voice is a unique service that is much more than a bare-bones telephone service. Its design is that you obtain a telephone number from Google (first one's free), or you port in a mobile phone number. This now becomes your single point of contact for inbound telephone calls and texts. It's a "virtual" number, in that it lives in the VoIP cloud, and it can be used via several different clients. When someone calls that Google Voice phone number, it can simultaneously ring:
- Up to six different 10-digit US phone numbers, known as "linked" or "forwarding" numbers
- Any Google Chrome Browser or Firefox browser that is signed into your Google account, on a computer with a microphone and speaker or a headset
- Android or iPhones running the official Google Voice mobile apps
- As many Polycom OBiTALK hardware products as you wish
Outbound calls can also be made from any of the clients listed above. Text messages can also be sent and received (US only). So, in practice, you can have a Google Voice number that works on a OBiTALK desk phone, your Android or iPhone, and your web browser, wherever you are.
The standard disclaimer applies: this is the (mostly free) consumer version of Google Voice. It is neither recommended nor intended for business use, although such use is not forbidden. Keep in mind that it has no direct customer support, things do break occasionally, and may take days or weeks to resolve. Any small cost savings you gain may be offset by loss of business or reputation if clients can't reach you. Also of note: if your job requires call logging and/or recording for financial industry regulations, don't use Google Voice.
That said, you can certainly give it a try, or you can instead use a paid ITSP, such as Callcentric,
voip.ms, Phonepower, etc.
Learn more about Google Voice in the help center:
https://support.google.com/voice/#topic=1707989You can also find me over on the Google Voice help forum.