Consumers Union endorses 'bill shock' legislation

"Consumers Union supports this bill because there are currently no requirements protecting consumers from being caught off guard by unexpectedly high cell phone bills," the letter said, signed by Parul Desai, a policy counsel at Consumers Union.

CTIA, the association for wireless companies, said in a statement last week that bill shock legislation could cause consumers "frustration and confusion."

"We know those outcomes are not Senator Udall's objective. We look forward to talking with the Senator about the many plans and tools that our carriers currently offer their customers so that those who want to monitor their usage are able to do so," it said.