That depends. Are you using an upgrade for the line currently using the iPhone 4 with unlimited data? If so, you will have to choose a new tiered plan. If you have another line you can use for the upgrade, such as one that is not needing a new device but is eligible (as in out of contract), you can upgrade on that line and activate the new iPhone on your line. You can also pay full retail for the phone, purchase a used device from another source such as eBay or Craigslist, or use the Device Payment Plan (NOT EDGE). With the device payment plan you make monthly payments toward the full retail price of the phone, but you can keep your data plan as you are not taking a subsidy on the phone. There is a $2.00/mo surcharge with this installment plan.
