1. When your phone is in a place where it doesn't have service.
2. When your phone has been cut off due to lack-of-phone-bill-pay
1.
Guy 1: Dude, want to go camping?
Guy 2: Sure, but I'm not bringing my cell phone
Guy 1: Why not, bro?
Guy 2: The lake is a dead zone... My phone is an electronic paperweight up there
2.
Guy 1: Brosef, I tried calling you yesterday but it went straight to voicemail... Turn your phone on!
Guy 2: It is on, but I forgot to pay my phone bill. My phone's an electronic paperweight right now