answer:There are a couple of considerations. Several carriers who have offered unlimited data plans in the past are using people’s upgrades as a chance to change their data plans. You can do several things related to this: 1. Pay full retail for the new phone (>$600). 2. Check your data usage online to see if the loss of unlimited data will really hurt you. 3. DO NOT buy the phone online (pre-order from Apple or your carrier), instead go into the store and ask the clerk how this will affect any unlimited data plan and if you will you be “grandfathered” in. Because you have been on the 3Gs, you might find the anticipated reduction in cost on the various iPhone 4s to be completely satisfactory for your use and may not lose any unlimited plan you may currently have.