A phone and fax line are provided when you sign up for a Virtual Office plan. These numbers can be set up directly from your digital mailbox in a matter of minutes.
On iPostal1.com:
If you have a Virtual Office plan, you can add additional phone and fax lines by clicking Phone and Fax Settings in the sidebar.
If you do not have a Virtual Office plan, you can change your plan by clicking mailbox settings in the sidebar, and selecting Change Plan under General Settings.