Yes you, or always needed a SIM Card and must be difference from your currecly
SIM Card networks, And important is that SIM Card needed most during in the process of unlocking the phone.

And also some phone needed to put the SIM Card instant into in phone before to use the Unlocking Code and to unlock the phone, And in this case the result of unlock it will automatically detect the next networks service which would let you should know that the phone had been unlocking or not,

And others some phones too, In the instant when about to enter unlocking code into the phone to unlocking it, you don't need to put a SIM Card before but after enter the unlocking code into the phone any next result you get it on the phone screen. And the next thing to do is that you need difference operators SIM Card and try it, and check the networks and outgoing call is working, if all these option working then the phone had been unlocking.

Since there is difference model or mark of phone to unlocking it's obligation for us to provided you instruction for you to unlocking your phone when order the Unlocking Code