iPhone 4s unlocked by AT&T but still not working in Thailand with AIS. How to fix?

Hey All,

I moved to Thailand and am trying to use my iphone 4s here. I contacted AT&T and they unlocked they phone for me (have verified the unlock 3 times now) and have emailed me with the directions to complete the process. Unfortunately it is not working for me. I put in the sim card for the Thai provider (AIS) and restore the phone and when it finished restoring it gives me the "SIM Not Valid" message saying "SIM Not Valid the SIM card that you have currently installed in the iPhone is from a carrier that is not supported under the activation policy that is currently assigned by the activation server. This is not a hardware issue with the iPhone. Please insert another SIM card from a supported carrier or request that this iPhone be unlocked by your carrier. Please contact Apple for more information."

The email from AT&T says this "We have reviewed your request and confirmed that the device may be unlocked. Please allow 24 hours upon receipt of this notification to complete the unlock process. " and I did as directed but it still is not working and I get the same message every time I restore it.

Please help! I am at my wits end with all this!

Thank you in advance!