I did it at an Apple Store. They activated on my dads number (who was eligible for $299 price.) I took out the SIM in the iPhone, put it in his Samsung phone. Came home and activated it with my SIM card. Called AT&T to remove data plan from my dads number. Done.
I need to talk to a different rep since the one I talked to told me I couldn't remove the iPhone data plan within 30 days or I would be charged full price for the phone...