You'd be surprised how many people don't turn their phones off and then back on again. I've talked to a lot of people and so many people have never turned their phones off ever, and if they have, it's because the battery died or something else happened.

But, I would agree, the phone probably just needs to be power cycled. And take the SIM out as well once off. However, it could also be a network issue, because Nextel is notorious for bad service and reception.