I just got off the Phone with AT&T. I added a line to get the subsidized price on the iphone 5 so I will need to swap the # of the Iphone 5 to my existing #. I asked if this could be done over the phone before I activated the new line and she said it could. I thought well that's good because it will save me a trip down to the at&t store on Friday. So as we were talking about the process she says since you have grandfathered features you have to be very careful to explain everything to the rep who does the swap because if you lose them they won't be able to put them back anymore. She said it would be very easy to leave the plan that is on the iphone 5 now and just switch the # over and if that happens you will lose the grandfathered plans. I told her of my plan to activate the phone on the new number and then go down to at&t store and get a nano sim for my existing line and just swap the sims. She said that would be safer as there would then be no way you would lose the grandfathered features that way. So I think I am going to stick to my original plan to activate the phone on the new # and then go get a nano sim and switch it out. It's not worth taking the risk to me. I thought some people might be doing the same thing so I wanted to let them know this info.