I am only able to see Service Management Service Desk from the product downloads screen. I need to be able to download all products including CA Service Catalog.
They were licensed under the global service management license which includes everything.
This means when you download the product: Service Management - Service Desk,
One of those ISOs is actually CASM - Service Catalog.
The name refers more to how you are licensed than the product name (which can be very confusing).
For 14.1 the ISO name is DVD03135250E.
If you add them to the cart then you should be able to pick only this ISO.