Where are we getting that the phone had no actual service? I was under the impression, based on the media reports, that the phone couldn't get phone calls because it was turned-off after Blaze disappeared. It wouldn't make sense otherwise for Blaze to borrow a non-working phone that couldn't make or receive phone-calls.
On the angle that his parents were punishing him for something by taking away his phone. I don't see that happening, Blaze is an adult and based on his father's background, education, etc he doesn't strike me at the type to punish his adult son by taking away a phone or car. My suspicion is that if Blaze had a vehicle of his own it's more then likely in Philadelphia not Calif. The borrowed cell phone, who knows why that happened but I think it's a red herring in this case, trying to figure out the deal with the phone won't help us find Blaze.