To play multiplayer you need a genuine serial key for the game. I am not sure how god works but if they didn't give you a genuine, never used before serial key for the game then thats pretty much like selling you pirated game.
I also got a call from airtel for this and after seeing how old and pathetic their games are I denied it without a second thought.
I maybe able to help you with multiplayer if you tell me how you received BF2 and installed it.
The only reason I went in for GOD was that it is complimentary with my Plan (Airtel - Turbo 1299) "I Think". Anywho, GOD partially downloads the game just enough to launch it, the connection to the server is very fast ~5Mbps and the rest of the game streams. They do have some games which are multiplayer like - Age of Mythology, but that game Sucks. I dont want to play a game which is a decade old. Also I checked for BF2 there is no option to enter the Serial. After downloading and installing using GOD, It just launches, there is no promp to enter the key.
And yes I have downloaded "Stuff" from the internet to the tune of 25 - 35 Gbs. That is not a problem
And a lot of people do have descent hardware to play a lot of games , well maybe not the latest one but atleast something which is less than a Decade old.
Then they have this multiplayer shooter called ROCK - the frekin game is free anyway to download and play online, why would I want to join GOD to play ROCK.
They need to think over their game plan, Its been a month or something like that since I got GOD subscription. I dont think I have even used it for a day. What a waste!
P.S. - I think there was someone here who represented GOD. If you read this please Help us Gamers man, we deserve better than this. We do want an Indian gaming service like yours, but dude , the Games on GOD just suck!