What does it mean if I call a cell phone and hear nothing?

I’m calling a friends Verizon phone. They may have not paid the bill on time or they may have blocked me, or heck maybe they’re out of service. But if they were just out of service wouldn’t the voicemail kick in? If they didn’t pay the bill wouldnt it say that the phone was temporarily out of service? When I call I hear nothing, no ring, no msg., no voicemail…nothing.