[cardboard60]

About a year and a half ago. I had a Samsung S7E on At&t.
I left after 17 yrs caused their service where I live is terrible.
Got the unlock code..
Went to Verizon.
Used the Verizon sims card, put it in the At&t S7E and used the unlock code and put the phone in the drawer.

Got a buddy that needed a phone.
Used smartswitch and copied his stuff to the S7E.
He can talk on the phone. But can't use email.
At&t emailed him and said the phone is locked.

I paid cash for the Carrier locked At&t phone.
And I'm still having problems with At&t and a carrier locked phone.
And it's not like you can walk into a At&t store and anybody can help you either.
No more carrier locked phones for me.

[Rukbat]

Have him check the APN. It has to be AT&T's APN, not Verizon's.

[cardboard60]

He's on at&t straight talk.
He called straight talk and got voicemail.
Left his phone number.

It's a At&t phone