Why Dropbox Fax assigns a number when porting

When you sign up for a paid plan it automatically comes with a temporary number for you to use. If you want to port your number, please fill out our Porting Request. Once we get the information we need from you, we'll begin transferring your number(s).

The porting process can take up to two weeks, but there's no interruption to your service during that time. After your numbers have transferred, you can keep the temporary number or get rid of it, the choice is yours!