Porting your wireless phone number to another carrier will require you to provide a current account number and PIN for that number. These two seemingly simple items delay more ports than any other error or issue we see.
Most carriers do a good job of providing you with an easy way to get your account information (on your bill, online account, etc), but there are a select bunch that make it a little more difficult than others. Here's a resource that walks you through how to find that information:
Otherwise, it may be best to contact the carrier to get your account number and PIN if it's not readily available on your bill or in your online account.
Also, keep in mind that many wireless carriers have both an account PIN and a transfer or porting PIN. We need your porting PIN in order to port your number. If you submit your account PIN, the request will likely be rejected.