Why has my Lumia 635 not received the Denim update?

[Windows Central Question]

why is my lumia 635 has not received the denim update?

When I press check for updates it says my phone is updated. Is it because my phone is unlocked? In extra and info...it says Lumia cyan...At&t carrier

 

[xandros9]

AT&T GoPhone versions of the 635, like the one I have as a guinea pig apparently do not have access to that update. That is if your device is ATT branded.

If it was bought unlocked and isn't ATT branded, then I'm not sure.