I recently bought a at&t iphone 4s on craigslist and the seller said he was unsure if it was unlocked. So to check I took my Straight Talk Sim card out and put it in the iphone. I made a local call and the call went through, so it can call out etc. I know straight talk is affiliated with straight talk so I am still unsure if this will work overseas on a gsm network. But when I tried to access the internet I got a message saying "could not activate cellular data network" "You are not subscribed to a cellular data service. Can someone tell me if this phone is unlocked for the internet. I am not putting the iphone it on the straight talk network, so I did not call them with my sim number etc, all I want to know how can I tell if it is completely unlocked before I mail it to a a friend in India. Thanks in advance for any help.