I got a iPhone as a gift but still have my droid, can i switch?

I got a iPhone as a present and my droid is still under a contract. But i would like to switch to the iPhone but still be on my same contract, is there any way i could do that? Just switching phones and possibly switching to unlimited but not renew my contract. SOMEONE Please EXPLAIN.

Added (1). I also forgot to mention how to do it, i have Verizon Wireless

Cell carriers don't really care what phone you have as long as you are paying the bill. Assuming the phone is compatible with the carrier or unlocked, you could just swap your SIM over. IF the phone doesn't have a SIM or a SIM that isn't compatible with your droid, you can go to the store and they wil activate it for you.

Sometimes they can do it over the phone.

Yes, all they care about is that you finish your contract no matter what phone you use.