I'd like buy my new iPhone through Apple's iPhone Upgrade Program but I want to keep my same carrier and service plan. Is this possible?
Yes, you can keep both your carrier and your same service plan if you get your iPhone through the iPhone Upgrade Program. However, if for some reason your current plan does not include a data package, you will have to add one. Also, corporate and prepaid service plans are not eligible, so if your service is paid for by your employer you won't be able purchase an iPhone through the Upgrade Program and keep that plan. See here for more information on joining Apple's iPhone Upgrade Program.