AT&T unlock portal doesn't recognize my IMEI
I have a cell phone that was locked to AT&T and I'm trying to unlock it. However, when I enter its IMEI number (*****) into AT&T's unlock portal (https://www.att.com/deviceunlock), it says:
Looks like the IMEI number you entered doesn’t match an AT&T device. Try entering it again. Dial *#06# on your mobile phone to make sure you have the right IMEI.
But I double-checked the IMEI and it is indeed correct.
Is this something AT&T can still help with? The phone model is iphone xr