I have 4 question 1. can I use BSNL TYPE 4 modem ( with wi fi) on Airtel connection2. Why is Airtel charging 5000 rs for wi fi kind of modem where as BSNL charges just 2000rs.3. For basic ADSL modem ( with 1 ethernet and 1 usb) , BSNL is charging 1200 where as airtel 2000 Rs, whys is this big diff.4. Seeing the high cost of Airtel modems If I have to buy it from outside , which model, brand should I go for and what wud be the cost.