@GG, go to Settings - Wireless & Networks - Mobile Networks.
Under Mobile Networks, first select Data Enabled. Then select Use only 2G Networks. Lastly, select Access Point Names. Select the Zain/Airtel settings. Edit the APN, Proxy, Port, Username and Password as per the Airtel settings. I had to check online since am not an Airtel sub.
That should work.
Luck is when Preparation meets Opportunity. ~ Lucius Annaeus Seneca