3g sim card into 4g phone

[horsedoctm]

I'm buying a used Droid Razr 4g and currently have a Droid Pro. Can I take the sim card out of my pro and put it in the Razr and will it work? I'm trying to avoid going to Verizon. I want to be able to use the new phone tonight, I'm excited.
I'm due for an upgrade in 6 weeks, but aren't going to use it, because first of all I cracked the screen on my Pro last week, and secondly, I have the unlimited data plan and don't want to lose that.
Thanks for any help!

[bsweetness]

No, it won't work. The 3G SIM card in your Droid Pro is only there for international roaming. It doesn't actually authenticate the device while in the U.S. With LTE devices, the SIM card is actually required in order to register and authenticate the device on your account and on the network (something the 3G SIM card from your Droid Pro won't do). So, you'll have to get a LTE microSIM from Verizon in order to activate and use the Droid RAZR. If you go to a corporate store, it won't cost you anything, and you'll be up and running in no time.

[horsedoctm]

Thanks so much for your reply; I went by a store and got the card. I love the phone!!! It is awesome! Of course I'm still getting it figured out, but so far it puts the Pro to shame. ;-)