I don't have the storm 2, but been using a 8320 for a while and figured out that even when connected to wifi, it will only use wifi when connection to mobile network is weak. To get around this you have to select "wifi preferred" under your mobile network options. Then go to service status and it should show that you are connected to BIS via wifi. Also, your wifi indicator should now be lit up. Hope this works.
Edit: if it doesn't light up, power off (not a battery pull) and power back on.
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