Your devices are showing active with Sprint. When you try to activate another SIM into these phones it won't work due to it being active with Sprint. The device itself is assigned to your account. You can't swap out SIMs unless you deactivate the phone from the account.
We would have to do the swap for you on our end. You can also go to your Sprint account online to do a phone swap. You need another device to swap it too.
The device we just swapped off the account is unlocked. I doubled checked it. I would maybe reach out to Att, and see what they can do. You might have the wrong SIM for the phone.
No, att sim just comes from the new phone swap to. Also I cannot use another China sim card, which worked fine in another phone.
By the way, I have the identical phone, same model,same brand