I am old customer of airtel 4g.
I want to say something about how to use 4g Internet on your 2g pack? you will thinking that it is possible. but I can say yes it is possible. first of all you select 4g network on your device after some time you will see that your device show 4g network .
One main small region that on 2g pack 4g network require 10 mb at 1rs from your main account.I think it is not more for 4g speed Internet . on this pack you will downlaod any think at speed of 1mb/s to 2 mb/s continuously. when your balance become low then your 4g network will do not work.thanks.