VIENNA, Va. – The abrupt shutdown of Internet phone carrier SunRocket left more than 200,000 customers scrambling for alternate service Tuesday and raised questions about the viability of other standalone Internet phone providers.

SunRocket, like other companies that only provide phone service over broadband, attracted customers with cheap plans and innovative features. But traditional phone and cable companies also lowered prices and started bundling their services.

The competition proved too much for the No. 2 standalone Internet phone company after Vonage Holdings Corp. SunRocket ceased operations without warning on Monday.

Nobody at SunRocket was available to explain its quick exit. SunRocket Chief Executive Lisa Hook did not return a call seeking comment Tuesday.

At the company’s Tysons Corner headquarters, the phones went unanswered, the doors were locked and a cardboard sign with “Out of Business” scribbled on it hung inside the glass front door. The lights were on inside, and computers and fax machines remained in place, but all the artwork had been stripped from the walls.

Customers are out of luck. Many paid for their service well in advance, drawn by aggressively marketed service plans that cost $199 a year. It was not clear whether SunRocket customers have any recourse with government regulators.

Bill Adler, a writer and book packager who first reported the problems to the citizen journalism site NowPublic.com, relied on SunRocket for both his home number and a separate business line. Between the two lines, he estimated that he paid in advance for 18 months of service that he will not receive.

He is switching the numbers to another VoIP provider, but was told that could take as long as three weeks.

“Hundreds of thousands of people rely on this service,” said Adler, who is relying on a Verizon line that he kept as a backup. “To not give people two weeks’ notice … is really irresponsible.”

SunRocket’s customer service line offered callers a brief recording: “We are no longer taking customer service or sales calls. Goodbye.”

Adler admitted he’s concerned that the new VoIP provider will go belly up just like SunRocket did, but he’s enough of a fan of VoIP features, like e-mail notification of voice mail messages, that he decided to take the risk.

Meanwhile, a California company that is overseeing SunRocket’s liquidation, Sherwood Partners LLC, said it is in talks with other service providers to take over portions of SunRocket’s customer base. Sherwood spokesman Martin Pichison said he hoped to have such deals in place by Wednesday morning at the latest. He acknowledged that SunRocket customers are currently cutting their own deals for service with other companies.

Pichison said he did not know whether any deals would include credit to customers who paid their SunRocket bills in advance.

Many of SunRocket’s customers will opt for Vonage or another VoIP provider, some of which are posting “Welcome SunRocket” offers on their Web sites, said Stephan Beckert, research director at TeleGeography, a Washington D.C.-based research firm.

“It will give them second thoughts about prepaying a year in advance,” Beckert said.

Customers who aren’t enticed by the prospects of bundling their phone service with their cable or Internet provider will be willing to consider standalone VoIP companies because of the price advantage, he said.

SunRocket attracted more than $60 million in venture capital funding, including $30 million a year ago, he said.

Beckert said he was surprised that SunRocket burned through its funding so quickly, but said VoIP providers walk a delicate tightrope. On the one hand, VoIP’s primary appeal is that it offers cheaper service _ sometimes less than $20 a month for unlimited calling _ than traditional providers. That makes it difficult to raise prices.

At the same time, aggressive marketing campaigns needed to boost a brand name and reach potential customers can wreck a bottom line.

In SunRocket’s case, customer growth started strong but faded in the last year. In the last three quarters, SunRocket’s growth began to lag behind that of the industry as a whole, according to numbers compiled by TeleGeography. As SunRocket faded, cable companies like Comcast Corp. took off.

“If you were betting on SunRocket, you were betting on a horse that was moving slower than the rest of the field,” Beckert said.

The leading standalone provider, Vonage, has more than 2 million customers but it also has faced slowing growth rates and financial losses. It suffered a legal setback earlier this year when it lost a patent infringement case to Verizon Communications Inc. and a judge issued an injunction barring it from signing up new customers.

The case is currently on appeal and the injunction has been stayed, but Vonage has warned in court papers that its viability is precarious if the initial verdict and sanctions are allowed to stand.

Internet phone carriers are not regulated as tightly as traditional carriers. The Federal Communications Commission said Tuesday that VoIP carriers are not subject to the same rules that would apply to traditional carriers regarding discontinued service.

State regulators are generally barred under federal rules from overseeing VoIP providers, said Andy Farmer, a spokesman for the Virginia State Corporation Commission, a regulatory agency. The commission received several calls from SunRocket customers who lost service, and all such calls are being referred to the FCC, Farmer said.

While SunRocket’s demise caught many off guard, there had been signs for several weeks that the company was struggling. It laid off a large number of employees July 3, just days after the firings of two top executives and the resignation of a third.

A service of the Associated Press(AP)