i have questions about unlocking my note 5

[the13bats]

We have been with at&t many years but for many reasons are considering jumping ship,
So i wanted to get my note 5 unlocked, after a few run around games with att i have the unlock code,

If i am understanding the unlock process i have to remove the att sim and install a sim from say t mobile and start my phone and then it will ask for the unlock code att gave me and my phone will be unlocked,

I am very OCD and i have questions i cant seem to find answers to hunting on google but i bet some of you can help me.

Why do i have to install a non att sim to unlock my phone?

After its unlocked when i reinstall my att sim will it function as it did before unlocking?

Many thanks
cheers
b

 

[psionandy]

Putting in a 3rd party sim starts the software mechanism that asks for the code....

And after you unlock the device you can put your original SIM card in and carry on exactlyas before, but now with the ability to use a different sim card any time you like

 

[lunatic59]

Just to be clear, once a phone is carrier-unlocked it remains that way forever. Unlock it and you can swap SIM cards with impunity.

 

[the13bats]

Many thanks,
Sounds good, now just to beg att into giving me the unlock code,