I have an 05 GMC Sierra I just bought 2 months ago. It has Onstar. I received an offer for 3 months free Onstar. But, when I tried to get it, I got a "no phone available" message. I called Onstar and they said I need to upgrade the 05 analogue system to digital. Has anyone had this done? I'm not wanting to pay for the upgrade just to get the free trial.