For Sierra Wireless devices you want to download the program called "Watcher". This comes directly from the manufacturer of the modem.
Using this you can select EVDO only.
For Novatel devices you use their own connection manager, Novatel Connection Manager:
Select your modem and get the SierraWireless " Watcher" HERE ... under the drop box " Select Carrier" scroll to the bottom of that list and select "Other"
For Novatel go HERE ...select your device and then the Novatel Connection Manager - NOT Sprint SmartView.
Now you CAN select EVDO Only for a connection.