If you own a 4G handset and are an Airtel user, login to your twitter account. Send a tweet using #GetAirtel4G to Request for a 4G SIM. You will receive a reply from @AirtelIndia handle along with a link where you will be required to enter your SIM delivery details. Stay relaxed while your 4G SIM finds your doorstep soon. Of course, you don't pay a penny!