A few days back I bought a new Aircel sim (I use Aircel for its internet services) and immediately after activation I received the Pocket Internet settings. The settings seemed to work and I was happy.
The following day I recharged with Rs. 98 the 30 days unlimited internet pack but was unable to connect. I remembered that the settings dialog on my phone (Nokia N900) had a different name for Aircel settings than what it was now, it was Aircel Online earlier but now it was Pocket Internet. I searched for the right settings all over the internet but did not suceed. So, I took a decision, delete all settings from the phone.
After deleting the settings I lost many of my settings but there was a single connection in the settings dialog, with aircelgprs as Access Point. Please see the below screenshots.
I am continuously connected to the internet now :)
Update: I observed that the latest settings for Pocket Internet uses aircelwap as the Access Point. The above settings still work though.