When you do inquire to your mobile phone provider to get a number so you can change phone companies you must ask them some questions so you do not get confused. You have to find out when you will get your port authorization code in the first place and what their own procedures are for issuing it to you. Then find out the date it will expire, and what will happen if you do not use it by the expiration date. You might want to ask them if it is no good and you still want to change can you then get another one to use.