As Louis mentioned in the following thread, there is no web service method that simply returns the service option names in the request:
Service catalog webservices to fetch all the service option in request
One way you could get this information is by calling getRequestItems, which returns all of the service option elements in the request (basically select * from usm_subscription_detail where request_id=<request id>). You would need to parse out the appropriate 'itemid' from the results which correlates to the name element and pass the same as input to the Catalog Web Service method getRateItemDefinition which includes the name as 'itemtext'.