The survey by the Federal Communications Commission found that more than a third of people who experienced such "bill shock" said their bills jumped by at least $50. And 23 percent said their bills soared at least $100.
Joel Gurin, who heads the FCC's Consumer and Governmental Affairs Bureau, said it is too early to say whether the FCC will impose broad new regulations on wireless carriers or push the industry to adopt voluntary consumer protection standards. But the commission is clearly ramping up oversight of business practices in a market dominated by four national carriers, led by AT&T Inc. and Verizon Wireless.
Two weeks ago, the FCC said it is considering rules that would require wireless companies to alert consumers before they reach roaming or data caps on their plans. The rules would be modeled after European Union regulations that require wireless companies to send a text message to customers who are running up roaming charges or approaching data limits.
The FCC also is looking into whether wireless companies give customers adequate notice about early termination fees, which apply when a service contract is broken before it expires. The new survey found that 47 percent of wireless customers who have calling plans with an early termination fee did not know the amount.
The FCC's survey findings were based on interviews with more than 3,000 adults from April 19 to May 2.