, with $4.75 million in the back from private investors, is ramping up its efforts to exploit the growing Voice over Internet Protocol telephony services market.

The funds will be used to expand operations, sales and customer service departments as well, the company said in a statement.

The investors were not identified. said the funds had been raised throughout the year.

“This funding allows to grow as a leading provider of telecom services to the small- and medium-sized business market,” said Henry Kaestner, the chief executive officer of “As more and more customers turn to Bandwidth for our VoIP service, we are dedicated to ensuring they receive a quality product that is supported by unrivaled customer care and professional service.”

Sales of VoIP services to both businesses and consumers are growing. Vonage, a VoIP provider to consumers, has more than 600,000 customers — up from 400,000 earlier this year, according to The New York Times. Cable providers such as Cablevision and Time Warner Cable are also moving aggressively into the VoIP market.

In the business sector, research firm InStat reported in August that more than 155 million “business IP” end points will be in operation by 2009, and of those 37 percent will utilize wireless VoIP phones.

Kaestner said mobility will be one of the focal points of its expansion.

Mobile handset integration and single sign-on for cell and office phone voicemail are among the new features plans to add, the company said.

The company offers its VoIP services across all 50 states, offering businesses an alternative to conventional phone service and hardware., which was launched in 1999, also packages a variety of services for companies seeking a single source for ordering network services while insuring prompt installation and service at competitive prices.