There are three ways to set up Internet voice calling.
Mr. Chambers said Cisco was now selling 2,000 Internet voice phones a day.
"Internet voice is not even cutting-edge anymore," Mr. Kaestner said.
By this she means banning operators from blocking services, as some mobile firms do to internet voice calls, for example.
When taken together with an Internet connection of dubious quality, an Internet voice call can become risky.
AT&T does allow other smartphones, including those that use the Windows Mobile operating system, to use Internet voice services.
In 2011 Microsoft bought the Internet voice communication company Skype for $8.5 billion, which at that time was the largest acquisition in Microsoft's history.
Skype is a leader in Internet voice and video communications, with 170 million users each month connected for more than 100 minutes on average.
Earlier this year, Ms. Kroes warned mobile operators not to block or hinder Internet voice services like Skype from their networks.
Revenue jumped 34 percent at the company's services business, a growing division that includes Internet, voice and other services for mostly small businesses.
The company's Internet voice service uses software that disguises signs of voice-over Internet traffic from operators, so the Internet calls can evade operators' filters.
