How are smartphones unlocked in street shops?

[rodion15]

I know a smartphone can be unlocked by either contacting the carrier or by using one of the websites that will do it for you for a fee.

I'm curious to know what do the unlocking and smartphone repair street shops use to unlock the smartphones. Do they just contact the carrier and do the job for you. Do they just use one of these websites?

 

[hassan6ka]

They put in a new software for unlocking.