Service catalog item, multiple request items, how to?

Created a catalog item with 3 groups of fields. There is a multiple choice variable (service type) which sets visibility (true/false) on each set of fields when an option is selected. (onChange)

There is an associated workflow that notifies the client based on the selected service type at submit.

The problem is that all 3 groups of fields are included on the request item, not just the ones for the selected service type.

How do I only add the fields associated with the service type selected to the created request item?