Since you "found" the phone, chances are the previous owner called customer care and told them he "lost" the phone or had it "stolen". Most likely, the
IMEI number of the phone has been blacklisted by NEXTEL so it will never be able to communicate to a tower again (receive a IMSI Authentication Ki/TMSI) until said customer unblacklists it, which as you know, AIN'T GONNA HAPPEN! Doesn't matter what
SIM you put in, valid or invalid, locked or unlocked, Boost or NEXTEL. You might find some unscrupuolus service reps. who would unlist it for you, but they will loose their jobs if caught. Your best bet is to 86 the thing and get a legit phone.
NO WAY JOSE! SAINT HAPPENIN'! CAB-NO, MAYBE? POSSIBLY IN RE-NO, TO PLAY KE-NO, IN THE CASI-NO.