Vonage, the fast-growing provider of Voice over Internet Protocol telephone services, will use Internap to help support is growing nationwide network, the companies said Tuesday.

Vonage now has more than 350,000 subscribers and is adding more than 25,000 new customers per month. The company offers long-distance calls at flat monthly rates.

High-speed Internet users can purchase Vonage starter kits at a variety of locations. The kit includes hardware from Linksys, which is part of Cisco Systems. Call plans start at $14.99 per month for individuals and $49.99 for businesses.

Internap will provide Vonage with Internet connectivity services out of Atlanta, where it is based, plus New York, New Jersey, Nashville TN, and Dallas.

“Internap’s premiere customer service, backed by the industry’s best performance guarantee enables us to efficiently manage our Internet connectivity, to guarantee our customers the best call quality,” said Jeffery Citron, chairman and CEO of Vonage. “They have a proven track record on which I am confident Vonage customers can depend on.”

Internap provides routing services designed to increase performance and reliability of Internet performance. It also includes several performance guarantees as part of product offerings.

“Vonage is clearly changing the paradigm for voice communications in this country,” said Greg Peters, president and CEO of Internap. “We are extremely pleased to be associated with Vonage. At Internap, we truly believe we are delivering the kind of technology that gives Vonage and hundreds of other enterprises around the world the confidence to deploy on-demand applications over the public Internet.”

Internap’s own infrastructure is linked to major Internet Service Providers around the world. It has major centers in Tokyo, London, Singapore, Hong Kong and Sydney Australia.

Also Tuesday, Vonage said it would begin selling its services through CompUSA at the technology chain’s 200 stores nationwide and online at Compusa.com.

Vonage’s services include caller ID, call waiting, voicemail, call forwarding, and emergency calling service.

Internap: www.internap.com

Vonage: www.vonage.com