You can turn off a carrier by setting to "inactive" if you do not wish to see rates. This is done right on the Carriers Page in your Shippo account.
1. Go to the Carriers Page by clicking on Settings and then Carriers at the left of the page
2. Click on the toggle button in the Active column to turn off
3. The account is now "inactive" and will not display rates during label creation
Alternate:
1. Click on Edit to the right of the carrier
2. Click on the toggle button next to Active to turn off
3. Click Update Account