AT&T has written a letter to the FCC saying that Google Voice restricts high-priced calls, such as those to rural areas. In such areas, local carriers charge high fees to long distance carriers in order to place calls. The law requires long distance carriers to pay the fees, though the carriers originally wanted to simply block access to high-priced areas.
Enter Google Voice. They are restricting access to high-priced calls, and AT&T doesn't like it. Thus, the aforementioned letter to the FCC. AT&T wants Google to be forced to connect the high-priced calls just like they are. AT&T also threw a jab, saying for as much as Google is lobbying for net neutrality, forcing carriers to provide access to the entire internet, they sure aren't practicing that same philosophy when it comes to Google Voice.
Google isn't denying that it restricts calls, and they shot back at AT&T saying that they're comparing apples (no pun intended) and oranges. Google reiterated that its Voice application requires the use of a landline or mobile plan to work in the first place. Also, they said that lobbying for net neutrality is about broadband carriers, not web-based software applications.