Problem:

To remove the  'This web service is using http://tempuri.org/ as its default namespace' message.

Resolution:

In the Net Express IDE, select 'File', 'Open Service Interface's.

Right Click on the Web Service

Select  'Settings'

Under, Service Name, click the  'Advanced'  button to bring up the 'Service Namespace settings'.   

What you put in here populates the field on the previous pane