Hi kevin38583. I'm so glad you've taken interest in our Prepaid services! We have a lot of fantastic devices that can be activated to Prepaid at www.vzw.com/prepaid. Since the Samsung Convoy u640 is a Push-To-Talk capable phone, it cannot be activated on a Prepaid plan. If you happen to purchase a non-Push-To-Talk capable device from an outside source, you can check the device ID at http://vz.to/U2wgl6 to make sure it's compatible with Prepaid service and can be activated on our network. Phones will either need to be a prepaid device or have been activated on post pay service for a minimum of 6 months before it can be activated to Prepaid service. There's also lots of great answers to other frequently asked questions about Prepaid service at http://vz.to/LlHur3.
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