3820169 - Why is the user/arranger encountering an error message Booker Phone cannot be null or empty?

The user is attempting to make a reservation. However, upon clicking on the Reserve and Continue tab. The user encountered an error message " We're sorry, we encountered an issue that prevented us from completing your request. Booker Phone cannot be null or empty."

When making a reservation the user/arranger is encountering an error Booker Phone cannot be null or empty after clicking the Reserve and Continue tab. , KBA , CON-CA-TLS-IEM-IMP , Import Credit Cards , CON-SRV-TRV-ADM-LAN , View Airlines , CON-MOB-TRV-HTL , Hotel , CON-SRV-TRV-RAL , Rail , Problem