I have the unlock code but the "Enter the device unlock code." screen doesn't appear, help please

I already do ann unlock request, after a couple days I got an email wich says "We approved your unlock request" also there was my unlock code, I follow the instructions of the email, I turned off my cellphone with a non-AT&T sim but the device screen with the message of "Enter the device unlock code." haven't appeared yet. I have never "root" or made modifications in my celphone, because is new. Please I need to travel to other countries so I need to use many types of sims, so please could you help me with this problem making the "Enter the device unlock code." screen appear in my celphone, or how could I search or find this screen in my device. Thank you for your help.