so my original charger that my iphone came with was acting little funky and i took it to the store to get replaced. they pulled a brand new one off the shelf and gave me it right out of the box and took my old one. my question is this. are the iphone chargers that come with the phone when you first get your phone the same as the ones they sell right next to all the accessories? just wanting to make sure i am getting the same Watts of power with this new charger as i was getting from my original charger. is their any difference in chargers?