ENGLEWOOD, Colo.--(BUSINESS WIRE)--CSG Systems International, Inc. (Nasdaq: CSGS), a leading global provider of interactive transaction-driven solutions and services, today reported results for the quarter ended June 30, 2015. Key Highlights: • Second quarter 2015 results: • Total revenues were $182.6 million. • Non-GAAP operating income was $34.9 million, or 19.1% of total revenues and GAAP operating income was $26.2 million, or 14.3% of total revenues. • Non-GAAP earnings per diluted share (E