I received an email from my carrier that my iPhone 5 is unlocked. I confirmed via a free IMEI checker on the web. Do I need to plug the phone into iTunes to complete the unlock? Or will a SIM card from any compatible GSM carrier work now? support.apple.com/kb/HT5014 suggests that all one needs to do is put in a SIM from the new carrier and complete setup process, no need for iTunes. Anyone done this?