Washington ? Despite static, dropped calls and dead zones, Jeff Danielson sticks with his cell phone service, not out of loyalty but because he can’t stand the thought of asking clients to call a new phone number.

“I’ve been unhappy with the service, but I’ve given up doing anything about it because I really don’t want to lose the number,” said Danielson, 27, a Washington technology consultant. “I’m afraid I would lose clients that way.”

Federal regulators are sympathetic with Danielson’s plight and have ordered cell phone companies to let people take their numbers with them when they switch to a competitor. The wireless providers asked a federal appeals court Tuesday to block the regulation, arguing that keeping the same phone number is a convenience, not a necessity.

The cell phone companies told a three-judge panel of the U.S. Court of Appeals for the District of Columbia that the Federal Communications Commission’s “number portability” rules will raise costs while doing little to increase competition.

“It’s very speculative to say this even offers consumer benefits,” said Andrew McBride, an attorney representing Verizon Wireless and the Cellular Telecommunications and Internet Assn.

McBride asserted the FCC overstepped its authority and made legal errors in its order. Retaining the same phone number is not an essential service like making wireless providers supply enhanced 911 systems to help authorities locate cell phone users during emergencies, he argued.

The judges are not expected to rule for several months. Without court intervention, the regulations are to take effect Nov. 24.

Congress decided in 1996 that people can keep their traditional local phone numbers when they change phone companies. The FCC decided soon after that wireless carriers should offer that same ability to people in the largest 100 U.S. cities by June 1999.

The FCC extended that deadline three times, most recently granting a yearlong extension last summer after Verizon Wireless asked the commission to eliminate the requirement.

“Wireless companies will have stronger incentives to provide better service and lower prices if consumers can take their numbers,” said Chris Murray, an attorney for Consumers Union, publisher of Consumer Reports magazine. He said small businesses and self-employed people were particularly harmed when switching carriers because they lose numbers known by customers.

Most wireless companies argue their industry is competitive enough and doesn’t need a regulatory boost. They say about 145 million people subscribe to U.S. cell phone systems, and about a third of them change carriers each year.

“The wireless industry is the most competitive telecommunications market on the planet,” McBride said after the hearing. He said the expense of providing the number switching service would take money away from better cell phone coverage and cheaper phones.

The wireless industry estimates the requirement will cost more than $1 billion in the first year and $500 million a year after that.

The industry also says the FCC’s number portability rules are unclear regarding traditional landline phone companies and give them an unfair advantage. The wireless companies want the FCC to declare that traditional landline phone companies must allow their customers to keep numbers when switching to cell phones.