How do i unlock a verizon samsung galaxy s4 to use an at&t sim card in it?

[AC Question]

I have at&t and i'm trying to use a verizon galaxy s4. i brought it to verizon and they said it was unlocked but i've followed steps on here exactly with the settings networks more networks etc. and have it set to at&t phone but yet it still has everything verizon on the phone and it is telling me i do not have a verizon sim card in and it can't be read?

there's a little sim card with a question mark at the top left of my screen.

I also don't understand the APN and stuff. I just really need helppppppppp ugh I'm going insane without a phone

 

[anon(632115)]

Swipe down the notification bar at the top of the screen. It should display no verizon card message , tap this and it should display a button "about app", tap this and on the new screen hit force stop. You may get a warning but do it and you should be good to go. Every time you switch off you will have to repeat the process

 

[Feldon]

If you have the Samsung Galaxy S4 SCH-i545 (Verizon) it will work fine on AT&T using 850MHz and 1900MHz bands (and LTE band #4).
If you have the Samsung Galaxy S4 SCH-i545L (Verizon) it will not work on AT&T no matter what you do.