EarthLink Inc (ELNK.O: Quote, Profile, Research) said SK Telecom (017670.KS: Quote, Profile, Research) (SKM.N: Quote, Profile, Research) would invest up to $270 million in Helio, their wireless voice and data services joint venture.Helio expects to end the year with between 200,000 and 250,000 subscribers. Helio expects a full-year net loss of $340 million to $360 million, EarthLink said in a statement. (Reporting by Jennifer Robin Raj in Bangalore)