We describe an empirical study of the creation of a Semantic Service Registry in the context of the Operations Support Systems (OSS) department of a telecom company, to address an emerging problem of finding the right services to build new business processes in a pool that steadily increases. We show how to obtain an ontology for the telecom domain to annotate services and thus benefit from semantic technologies to effectively find them based on description logics inference mapping. We designed and implemented a proof of concept for providing a matching degree even when the cardinality of the service elements of the query and the cardinality of the service elements being sought differ. This is relevant for web services reusability and flexibility. Our solutions are overviewed and a set of lessons learned are discussed.