So, after significant headdesking, it's working. Here are the steps:
Setting up a Google Voice business line to your personal cell phone:
(I did this with an iPhone 3GS, AT&T is my carrier):
1. Download iPhone app for Google Voice (so you can make calls from your phone as if from your Google Voice number. This won't actually affect your settings though).
2. Go to Google Voice on your browser and go into Google Voice settings:
Under the "Phones" tab, check "forward calls to mobile."
DO NOT check "activate Google Voicemail for this phone."
3. Under "Voicemail & Text" tab, record a greeting for Google Voice & name it whatever you want. When you click "record new," it will call you on your phone. When you answer, a recording will prompt you to leave a message. (You'll have the option of doing it over if necessary.)
If you want anything else -- voicemails transcribed, etc., check those settings.
4. Under the "Calls" tab, change the default to "Call Screening On" (note: I don't have the box checked for requiring callers to announce their name because I believe that hinders customer service, but if you want this, it won't affect the final outcome).
Caller ID radio button: choose "Display Google Voice" (then, on your phone, add a contact for your business line so whenever it rings, you'll see the incoming call from that business name. I personalized the label so it says my business name and "Google Voice" in small letters (underneath instead of "iPhone" or "home" or "work" or the usual labels).
Check "Place missed calls in inbox."
5. Last but MOST IMPORTANT step: on your phone, you must deactivate conditional call forwarding (which is set as a default):
On your phone, dial ##004# and hit "send." This will ensure that calls coming into your phone are not all going to forward to Google Voice (the conditional call forwarding default).
RESULT from all these steps:
- Calls to your business number forward to your cell. If no answer, they will route to business voicemail (or whatever you set as your Google Voice voicemail).
- Calls to your personal number forward to the same cell. If there is no answer, they will route to your personal voicemail.
I keep my phone on silent almost all the time to keep disruption down when working so it was important to me that the correct voicemail picked up for its associated number. I hope this information is useful if you're having problems setting up your Google Voice account.