Hello everyone. I purchased a Droid Ultra and I read here and elsewhere it can be used on Straight talk prepaid with an ATT nano Sim. I ordered the ATT Sim from straight talk and inserted into the phone. When the phone boots up it says unknown Sim. I have not activated the Sim or set up a straight talk account yet. Does that have to be done for the phone to properly know what it is? I didn't want to waste money on a straight talk plan if it doesn't work.