US telecoms giant AT&T has admitted that it struck a deal with Apple to prevent iPhone applications from using its network for VoIP.
VoIP allows voice calls to be routed over mobile internet but reduces a network operator's voice call revenue.
Apple and AT&T both responded to a federal inquiry into Apple's failure to approve Google Voice, a VoIP application for the iPhone.
Apple said that the app had not been rejected but is still under review.
In July, Apple rejected Google's application for the Google Voice app to be sold in its App Store, and removed several third-party applications that leveraged the same technology.
The app is already available on Blackberrys and phones that run both Google's Android and the Symbian operating system.
Apple's move prompted an inquiry from the US's Federal Communications Commission (FCC).