T-Mobile 3g Setup on Vigor 2820

Hello<br/>
Can anyone tell me how to configure the 2820 router for use with a T-Mobile 3g connection supplied with a Nokia CS-10 modem?<br/>
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The modem works fine connected to a PC and the router works fine connected to a land line. I want to use it as a backup connection should the land line fail.<br/>
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I have enabled WAN2, selected 3G USB Modem and set it to 'Always on' for now. However it is not connecting and I am not sure what to do with the other settings.<br/>
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Thanks for any help.<br/>
Peter