[qi:090] Five years after it launched Voicewing by rebranding DeltaThree, Verizon (s VZ) is shutting down the VoIP service that never managed to get any traction. It was launched to compete with Vonage. AT&T (s t) stopped signing up new customers for CallVantage, another Vonage competitor, in 2008. Voicewing will be shut down on March 31, and will most likely be replaced by FiOS Digital Voice, a new offering. The decision will almost certainly push DeltaThree over the edge — the company has been running out of cash and has already been delisted from Nasdaq.