NEW YORK -- AT&T said on Thursday that it will expand availability of Apple's (AAPL) FaceTime video application to all customers of its usage-based high-speed data services after its limit of the service to certain customers sparked a controversy.

Advocacy groups complained in September when AT&T made FaceTime available on its cellular service only to customers on its data share plans, which allow families or individuals to share a single data allowance with multiple devices.

The FaceTime video-conferencing application started to work on cellular networks in September after Apple made available its latest operating system, iOS 6. Before iOS 6, the service was only usable over Wi-Fi short-range wireless connections, which are often free to use but have a limited coverage range.

AT&T, the No. 2 U.S. mobile provider, said it has now decided to expand the service over the next six to eight weeks to all tiered-data customers, who pay for a set amount of data every month, as long as their device supports Long Term Evolution, its fastest data service.

However, FaceTime will still be blocked for customers on AT&T's unlimited data plan, which includes unlimited data usage for a flat monthly fee. AT&T has been working on phasing out these plans.

Jim Cicconi, its senior executive vice president for external and legislative affairs, said in a blog post on Thursday that AT&T had originally made the decision to limit the service out of caution because it was worried heavy use of FaceTime could overload its network.

"To do otherwise might have risked an adverse impact on the services our customers expect -- voice quality in particular -- if usage of FaceTime exceeded expectations," Cicconi said.

Cicconi did not say why the company had changed its policy.

Rep. Anna Eshoo, D-Palo Alto, described the decision as "a victory for consumers and for those who know a free and open Internet is vital to sustaining our rapidly expanding mobile technology market."

Advocacy groups Free Press, Public Knowledge and the New America Foundation's Open Technology Institute warned AT&T notice on Sept 18 that they planned to file a formal complaint with the Federal Communications Commission unless the company changed its FaceTime policy.

Public Knowledge said that the group would still pursue legal action against AT&T if it doesn't make FaceTime available to all of its customers quickly.

AT&T also said it began rolling out new billing plans designed to allow deaf and hard-of-hearing customers to make use of FaceTime.