Is a device Unlock Code required when changing providers? So... I just switched from AT&amp;T to Cricket Wireless. They gave me a new SIM, and AT&amp;T gave me an Unlock Code. I have an Android Samsung Galaxy Skyrocket S2.

I use Cricket Wireless.

I put in the new SIM, and was never prompted for a Code. I was able to get hooked up to the Cricket network and make calls just fine.

Am I good to go? Or will I be screwed if I don't get my Unlock Code entered?
You're good for now, but don't lose that unlock code!

Cricket is now owned by AT&amp;T, and you can use either an unlocked GSM phone or a locked-to-AT&amp;T or locked to Cricket GSM phone on Cricket. But if you should ever need to use that Galaxy S II Skyrocket SGH-i727 on (for example) T-Mobile, you'll need the unlock code!

To unlock a Samsung Galaxy phone, you just need to put a non-AT&amp;T, non-Cricket SIM card in it, and then power-on the phone. It should prompt you for the unlock code. If you don't have a non-AT&amp;T, non-Cricket SIM card, then just visit a T-Mobile store, and let them put one of theirs in it.

AT&amp;T has unlocking instructions here:
http://www.att.com/media/att/2014/support/pdf/ATTMobilityDeviceUnlockCodeInstructions.pdf