I just bought this phone on Flea-bay. It appears to be in excellent condition. It was listed as CDMA but I see it is also GSM. So it's asking for a SIM card when I start it up. I wanted to get it flashed for Cricket. Do I need a SIM card to use this phone? I realize Cricket is a CDMA network but what about the SIM card nag. What kind of problems am I going to run into with rooting and ROMS for this thing? Also I'm curious...Can this be unlocked and flashed at the same time?