Lumia 640 Unlocking problems

1) AT&T Lumia 640 GoPhone

I get code from at&t but it does not work. I put in my new zealand sim and turn it on and try unlock code on 10 attempts remaining screen and it says incorrect code then puk required, I then input sim puk then it says sim error.
I also try ##7820# method and it accepts code and padlock is opened but on reboot it is locked again.

2) Cricket USA Lumia 640

I paid for unlock code on eBay and it does not work on 10 attempts screen or ##7820# screen.

If anyone could help with either problem or point me to a guide to hack a registry or whatever I would be very grateful.

Thanks.

P.S. what happened to those little black multi -unlock sim things you could buy back in the days that slid in between your sim and the phone and could fool a phone?
Do they not work in this day and age?

Thanks.