Am I missing something in the SIP client?

I am trying to receive Google Voice calls which forward to my SIP. This sends Google Voice calls to me with no problems through my VPN.

Google Voice wants me to press 1 to accept or 2 to send to voice mail.

Only problem is, I can't find any dialpad when I receive the call to choose, and if I can get in to the menu and attempt to go to DTMF Dialing but then usually Google Voice hangs up on me and sends the person to voicemail.

EDIT: Just an update for people having issues withe workaround scripts. Don't be alarmed if SIP doesn't connect at first after running the VPN. I swore the scripts were not working but waited a minute and suddenly SIP was connected.