Default How to update

How can I update my moto g using 3G network. I have a notification informing software update. When I'm accessing that its saying to enable WiFi. As I have no WiFi network I can only update through 3g network. And when I'm trying to update via system update tab under settings menu its saying an "an update being downloaded, you will be notified when it is completed". But I'm checked my data usage for last 3 hours , I can't see any serious data ranger transferred.. So how can I update.. Help me

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