(Those Device are sold by Walmart, Target, Bestbuy, etc... Basically any AT&T Reseller)
When you run a GSX Check report, it must show:
Initial Activation : 4000 US Reseller Flex Policy
Applied Activation : 23 US AT&T Activation Policy
Next Tether : 23 US AT&T Activation Policy
These IMEI's are the ones who will not get unlocked using clean service or premium service, but you know they are AT&T.
A common error is: "The IMEI you entered does not appear to be an AT&T wireless phone or tablet." when using AT&T Clean Service.
This is a special service for those IMEI'S, but you must first run a GSX Check report and make sure it shows: "4000 US Reseller Flex" for initial activation
Device must be activated FIRST with an AT&T SIM Card.
DO NOT SUBMIT, TMOBILE, TRACFONE OR NOT ACTIVATED PHONE, ETC.
THIS SERVICE ONLY SUPPORTS DEVICES ACTIVATED WITH AT&T
THIS SERVICE DOES NOT SUPPORT LOST/STOLEN DEVICES, OR FRAUD DEVICES - NO REFUND FOR ANY MISTAKES