Verizon Wireless has relented to criticism from privacy advocates – including members of Congress – and is allowing customers to opt out from a mobile advertising program that tracks web behavior. The company made the announcement this week.

Known as “supercookies,” customer codes had been subject of debate as Verizon implemented its mobile ad program. The codes enabled third parties, advertisers in particular, to “exploit Verizon’s persistent tracking to continually follow a user’s web browsing activities,” The New York Times reported.

Earlier this week, four Democratic members of the U.S. Senate’s Committee on Commerce, Science and Transportation sent a letter to Lowell C. McAdam, Verizon’s CEO, outlining their concerns with the telecom’s data privacy practices.

The scathing letter mentioned “supercookies” specifically. “Because of the threats to consumer privacy, AT&T wisely discontinued the use of similar mobile trackers, while Verizon has chosen to carry on,” the senators wrote.

Verizon announced its decision to let users opt out just one day later, The Times reported.

“We listen to our customers and provide them the ability to opt out of our advertising programs,” Verizon spokeswoman Debi Lewis said in a statement. “We have begun working to expand the opt-out to include the identifier referred to as the UIDH, and expect that to be available soon. As a reminder, Verizon never shares customer information with third parties as part of our advertising programs.”

San Francisco-based digital rights group Electronic Frontier Foundation has circulated a petition to prod federal agencies to take action against Verizon and its partner in the mobile ad program, a digital marketing software firm called Turn. The petition has garnered more than 2,000 signatures so far.