Complex sentence: Columbia's ties to Edison and the North American Phonograph Company were severed in 1894 with the North American Phonograph Company's breakup, and thereafter sold only records and phonographs of its own manufacture.
Split into simpler sentences: Columbia's ties to Edison and the North American Phonograph Company were severed in 1894 with the North American Phonograph Company's breakup. Thereafter it sold only records and phonographs of its own manufacture.