The Voicesafe is only able to display the number that it is receiving from the phone systems caller display.
If all calls outbound are being displayed as Withheld by the phone system then the Vociesafe will in turn display as Withheld, as shown below.
To fix this issue, you will need to ask your phone system support company to enable caller display on all extensions. For example if you have an extension 100 ask your phone system support company to enable the caller display to be 100 instead of Withheld.