UnAssigning Tracking Numbers to Campaigns can be done in the Campaign's Window.
From the Main Menu, Click on Affiliates -> Campaigns.
Open the Campaign Window by clicking on the Campaign Name.
Under the Campaign Information you should be able to see if there is a number assigned to this Campaign.
If there is a Tracking Number assigned to the campaign, you should be able to unassign it by clicking on the icon 
Click Yes to Unassign the Tracking Number from the Campaign.
Note: Calls to Tracking Numbers that are not assigned to any Campaigns won't be Routed to your Platform.