Go to Google Play store (formerly known as the Android Market) and download the free app called "4G Toggle" by the developer named We Make Better Apps. Then add this shortcut to your home screen. Choose the option where it will take you directly to the settings screen where you choose "Network Mode". Change the network mode to "CDMA only" to force the Rezound to stay in 3g mode.
Or you can do this the long way :
Settings --> Wireless and networks - - > Mobile Networks - - > Network mode --> choose CDMA ONLY
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