Updated

Verizon Communications Inc. has told customers it is shutting down its VoiceWing Internet-based phone service to focus on other technologies.

VoiceWing will be permanently shuttered on March 31, the phone company told customers in a letter last week.

Those who want to keep their phone numbers can move them to other services, but the process may take up to three weeks, so there's not much time to find an alternative.

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As with AT&T's CallVantage and the phone services of Vonage Holdings Corp., VoiceWing subscribers got a small adapter that allowed them to place calls by connecting a phone to a broadband Internet line.

Such Voice over Internet Protocol, or VoIP, services sprouted up in the early years of the decade, but have lost steam amid persistent problems with audio quality and a patent litigation offensive from phone companies, including Verizon, against market leader Vonage. Cable companies, meanwhile, have used similar technology to successfully introduce their own phone services.

Deltathree Inc., the VoIP company that ran the back-end services for VoiceWing, is running out of money and has seen its stock delisted from the Nasdaq Stock Market.

The shutdown of VoiceWing "was a business decision based on a number of factors including the strategic fit of the service in our evolving digital voice portfolio," said Verizon spokeswoman Bobbi Henson.

The New York-based company recently announced "The Hub," a multifunction touch-screen home phone that connects to a broadband line. It is also planning to introduce a VoIP service for customers on Verizon's own fiber-optic connections. VoiceWing was available to anyone with an Internet connection.

Henson said VoiceWing was "a niche service that was never mass marketed." The company does not disclose how many customers VoiceWing has, but Henson said it was not material.

AT&T Inc. stopped signing up new subscribers for CallVantage last summer.