I looked at the SipGate Rates page
and noticed this that may be causing the confusion:
The applicable rate depends on the number dialed - not from where you are calling.
The rates only apply to outgoing calls. You get unlimited incoming calls to your SipGate phone number that is free. However, outgoing calls go out directly through Google Voice. So we never make an outgoing call from SipGate. My outgoing calls log on my SipGate profile is completely empty. But my incoming calls log shows both my incoming calls and my outgoing calls... Here's why.
When I make an outgoing call, Asterisk sends the number I dialed, plus my SipGate number to Google. Google then places two calls, one to the number I dialed, and one to my SipGate number. Asterisk then merges those calls together and I start hearing rings on my phone. It takes a couple of seconds for this all to take place, but that's not much worse than a traditional phone line.
Hope this clears up the confusion...