After gaining the unlock code from your carrier, I've been told you need to insert a sim card to get the screen pop up to input the unlock code for your device. I'm curious about a couple of things here. A) Does it matter what kind or brand sim card I purchase to unlock the phone? Was thinking of buying a cheap TMobile one from Amazon if that'll work. B) If it does matter, can you make any GSM carrier recommendations(or warnings to stay away from) other than Cricket? Thanks all.