Assuming the problem is net-connection priority, that's actually not a good way to solve it.
The official way: open up your Network Connections control panel (the one that shows all your adapters), press Alt, select Advanced, and then select Advanced again. In this window you can alter the priority of your net connections.
edit: That said, Wifi connections are normally defaulted to be the top priority, but perhaps this is not so for cellular modems because of providers charging by the kilobyte if you go over your plan.
Think for yourself, schmuck!
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