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ATT has unlocked my iPhone and will be doing the remaining steps detailed in here http://support.apple.com/kb/HT5014?viewlocale=en_US&locale=en_US
I find it unnecessary to erase and restore my device before and after using a non-ATT SIM card. I will surely backup my device but will there be issues if I skip the erase and restore steps (step 3 and 5)?
restoring the device is the only way to start up the new activation policy (your unlocked policy), so if you don't do the restore, it won't really be an unlocked phone

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