I am useing Vodafone sim is very power full network in any place in kolkata and its 3G network is grate and fast then Airtel, Reliance, Idea, Tata docomo and aircel . and Vodafone launch 4G network is very good in kolkata is 4G network speed is 4 MBPS in any browser and Vodafone 4G network is very very better then Airtel 4G network and My Vodafone App & Vodafone M-PAISA is very usefull. I used Vodafone sim is Samsung Galaxy Grand 2.