By 2005, 12.5 million people will buy local phone service from their cable operators, generating annual revenues of $2.67 billion, according to a study by the Washington-based Strategis Group. That's a massive increase over the 300,000 local cable phone customers who are expected to generate $133 million this year. According to the study, Cox Communications has the most telephone customers with an estimated 134,300, followed by Media One with 94,000 customers. Total cable telephony revenues will grow from $485 million in 2000 to almost $3 billion in 2005, Strategis predicted. The projections are based on the marketing muscle MSOs are putting behind phone service.