Airtel rocking free on Opera Mini For Android, Java and symbian Devices.

First Create Connection Settings with below IP and port
IP: 82.145.211.1 
PORT: 80
Apn: internet.ng.airtel.com
Launch your Opera mini and input below:
Custom HTTP Server: http://dataportal.ng.airtel.com/cgi-bin/nph-proxy.cgi/010100A/http/server4.operamini.com:80
Custom Socket Server: socket://196.46.244.32/cgi-bin/nph-proxy.cgi/010100A/http/server4.operamini.com:80
Frontquery: dataportal.ng.airtel.com/*
Host: server4.operamini.com
Click Save and allow your Opera mini to install.

FOR S40 OR JAVA PHONES USERS 
Create Prov with the above IP and Port and activate it as a default setting.