maninder4k, you were spared for so long by Airtel, I am surprised actually. It has been around 6 months or so when people were reporting that Airtel has finally started capping their plans. Before that the cap was just on paper, in practise people DLed to their hearts content. Soon everyone on Airtel fell under this blanket.
If you give your friends number, they will most likely revert his connection to one like you rather than give you a similar plan.
Also for all to check how many GB are left, what do you use?
I am currently relying on this link which is not actually meant for checking usage but it gives the info nevertheless,
Smartbytes Packs - High Speed Internet Broadband Connection: airtel
Your DSL ID xxxxx_kk
High speed data transfer limit 75.0
GBs left in your account 37.8
Days left in the current Bill Cycle 5