We might call it something else, but I think we have something similar in the USA as they do in Australia where you have to get a Pac code or what is also called the port authorization codes and is simply the number which will identify you as owner of your mobile phone number. Some find it hard to understand needing it but with so many people doing unscrupulous things anymore it is to your advantage to do what they say. Besides you can’t transfer it if you don’t. They won’t allow it, no one can get away with not using it either no matter who they are.