This is going to be a super news for the users of at&t Lumia 920. As the 6-month exclusivity of Lumia 920 with at&t has recently expired (920 was launched during Nokia World, last year), at&t has officially started unlocking the device.
If you’re going to fly abroad or just want to use a different carrier within the US, all you need to do is get in touch with the at&t customer rep over phone, email or chat and ask for the unlock code. You will be needed to provide the IMEI number of your phone being the unlock codes are specific to an IMEI.
As the Lumia 820 was launched alongside the Lumia 920, seems it should also be ready for unlocking now. Though not very sure, it is still worth contacting at&t as maybe that’ll bring a big smile on your face.