Unlocked Lumia 521 with ATT Sim--cyan update?

[Windows Central Question]

I have an unlocked Tmobile 521 and recently switched to ATT for better coverage in my area. The 521 has not been updated with Cyan, but ATT has updated its 520 (the ATT version). Is there anyway I can get the Cyan update now that I'm on ATT?
Thank you.

 

[Pacus1x]

Sadly no, the 521 is tied to T-Mobile and the flash ROM (Essential configuration of the system) is different than 520, even those phones share the same hardware.

The only option you have is to wait the end of November for 521 Cyan update... that's the date given by T-Mobile.