I will be giving my old iPhone 4 to my son and I will be activating a new iPhone 5 on the same cellular plan. Will using the command - erase all content and settings" mess up his cellular plan?
It won't mess up the plan, it will just do what it says - erase the content (all the downloaded things like music, apps, contacts) and the settings (will send them back to default)
Normally not. Your cellular plan depends on the sim card that you use. Your son could set up as a new phone with his own apple ID and the old sim card.
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