From the Dashboard, click on Account and select Inbound Numbers from the drop down.
In the Manage DID section, Search for the Inbound Numbers.
Select multiple Inbound Numbers by clicking the check boxes.
If you want to select all of the results, click on the check box beside the Name Column
Click on Edit Selected DIDs Button
Edit DIDs section will appear, changes done here will be applied to all the DIDs selected.
Click on Apply Changes