Complex sentence: The company is marketed and trades as O2 (typeset as O 2), and known previously as Esat Digifone, The company was acquired by Telefónica in 2006, and is a subsidiary of Telefónica Europe.
Split into simpler sentences: The company is marketed and trades as O2 (typeset as O 2). Previously Esat Digifone, it was acquired by Telefónica in 2006, and is a subsidiary of Telefónica Europe.