Hi, I have an iPhone 4 that is eligible for upgrade. I want to apply its upgrade to another line, but when I go to order the phone I want, it requires that I upgrade the line with the iPhone 4 to an LTE data plan. What should I do here?
As far as I know, you have to upgrade the data plan to be compatible with the device that you are getting. Once you get the new device, take your current phone and the new phone to an AT&T corporate store and tell them that you did a cross-upgrade online. You want to get the proper SIM cards for each phone and have the proper data plans on each line where the phones will actually be used. The store should be able to take care of this for you.
This type of upgrade situation is usually easier to take care of in a corporate store than online for reasons like this.