Complex sentence: Afterwards, AT&T, reduced in value by approximately 70%, and continued to operate all of its long-distance services, although in the ensuing years it lost portions of its market share to new competitors, such as MCI and Sprint.
Split into simpler sentences: Afterwards, AT&T, reduced in value by approximately 70%, continued to operate all of its long-distance services. In the ensuing years, it lost portions of its market share to new competitors, such as MCI and Sprint.