NEW YORK — Cable TV providers who offer telephone service ranked highest in customer satisfaction in five of six U.S. regions, surpassing traditional phone companies among people who subscribe to national calling plans, according to a study by J.D. Powers & Associates.

Overall, however, customer satisfaction continued to decline while the average monthly bill rose again, with traditional phone companies charging substantially more than cable providers, the national survey released yesterday found.

Cox Communications Inc., which a year ago was the only cable company to take top honors in just one region, ranked highest this time in half of the six regions defined by J.D. Powers: the Northeast, West and Southwest, the customer satisfaction survey found.

Verizon Communications Inc. was the only traditional phone company ranked highest in one of its territories, leading the Mid-Atlantic region. Time Warner Inc. led the North Central region and Bright House Networks held the top spot in the Southeast.

The rankings did not include Vonage Holdings Corp. and other providers that use the technology known as Voice over Internet Protocol even though many of the cable companies ranked in the study do rely on VoIP to connect their customers.

While Vonage now has more than 1.6 million users, that customer base is spread too thinly across the six regions to measure against the more concentrated clientele served by cable and regular phone companies, said Steve Kirkeby, executive director of telecommunications and technology research at J.D. Power.

The attributes used to rank the carriers included reliability, billing, customer service and promotions. The study was based on responses from 12,196 customers nationwide who receive their local and long distance telephone service from one provider.

"While telephone service offered by cable companies is relatively new to the market, large numbers of customers are being lured to switch with enticing cost savings and highly attractive bundles of video, voice and data service," Kirkeby said in a statement.

But despite growing price competition from cable and pure VoIP providers, overall spending on local and long-distance service as reported by customers increased to $52.40 per month compared with $50.70 in last year's survey, an increase of 3.4 percent.

Notably, customers of cable phone service reported paying an average of just $42.40 per month, while the average bill from traditional phone companies such as Verizon, AT&T Inc. and BellSouth Corp. was $53.59.