Thanks to its relentless marketing and low prices, Vonage has quickly become synonymous with phone service over the Internet. But when Brandon Sehlke and his wife, Jennifer, moved into a new home in San Antonio two weeks ago, they chose a new Internet phone service from Time Warner Cable, not Vonage or AT&T, his old provider. Skip to next paragraph The deal Time Warner offered was just too good: phone service with a television package and a broadband connection for a promotional price of $89.95 a month. "Getting all three services was better than anything else we could find," said...