Vonage captured the lion's share of the VoIP business with a 53.9 percent market share. Far behind, in second and third place were Verizon VoiceWing and AT&T CallVantage, each with a 5.5 percent share.
More than 27 percent of subscribers cited network quality as the primary reason for switching to VoIP, Telephia said.
"Service providers who offer the best customer experience through superior product quality and excellent customer service will beat out their competition," Kanishka Agarwal, Telephia's vice president of new products, said in a statement.
"With a large share of U.S. households now connecting via broadband networks, VoIP has become a popular and cost-effective alternative for replacement, as well as a complement to the traditional home landline."