PackageHub supports two methods to disconnect your Carrier Account:
Disconnecting Carrier Accounts via the PackageHub Shipper Portal
After logging into the PackageHub Shipper Portal, click on Apps in the Navigation and click on the app. You can expand the Carrier Account section.
Click on the 3 dots to the right of the Carrier Acccount you wish to disconnect. Click on Delete and a modal will appear that will prompt you to the Carrier Account.