I have nextel i730 cell phone...powers up fine, tower says signal is excellent, but can not call out or in. Message on screen says "call failed...system busy , try later" . When I call my cell from land line...it goes to my voicemail. Is problem with my phone or with the service? Has been this way all day.

Both. Go ask about it. I'm not really sure my sister has the same problems. They had to do something not really sure sorry. Sprint & Nextel store try?