just a small walkthrough using my k500i ; hope this helps
--------------------------------------------------------------
go to menu->connectivity->internet settings -> internet profiles
select new profile ,then enter a name "AIRTEL"
then select-"connect using" and select "new account"
in the account type select gprs data , enter a name for the account->"gprs"
click on continue
now on the new window ["new gprs data"]
enter the apn as airtelgprs.com
then save
now a new data account "gprs" will be shown in the "data accounts" window
select "gprs" and save now a new profile "airtel" will be created
u can connect using that profile to avail airtel gprs