As you may know, Google Voice, the in-beta, Web-based calling service, has been blocking calls to some rural telephone exchanges with high access fees.

The fact that Google is blocking some calls is nothing new -- the company's decision has attracted the attention of several U.S. lawmakers from rural states and the U.S. Federal Communications Commission since AT&T first complained about it late last month.

But in a recent filing, AT&T starting giving examples of groups blocked from receiving Google Voice calls: an ambulance service, a church, a day spa, a tribal community college, a U.S. representative's campaign office, and even a convent of Benedictine nuns.

All of this probably cries out for another explanation of access charges. It's complicated, but access charges are what traditional voice carriers charge each other for carrying each other's traffic. Some rural telecom carriers charge high access fees to subsidize the cost of their networks -- in 2007, AT&T complained that some rural carriers were charging other carriers as much as $0.13 a minute. That can add up quickly these days, especially when many phone customers don't pay per-minute charges for long distance.

It's all perfectly legal, at least so far, but some businesses, namely sex chat lines and free conference-calling services, have taken advantage of the high access charges. They drive traffic to the rural carriers' networks, the rural carrier collects access charges, and the conference-call or sex chat service gets a piece of the action, so to speak.

AT&T, in its recent complaint to the FCC, also seems to put some words in Google's mouth. In a series of "truths" about Google Voice, AT&T says that Google claims it's only blocking calls to sex chat lines and free conference-calling services that take advantage of the high access fees.

That's not quite what Google has said. Google has acknowledged blocking calls to some rural telephone carriers that also partner with sex chat or conference-calling services.

AT&T has complained that Google is playing a little loose with the facts as well. In a blog post Oct. 9, Google telecom counsel Richard Whitt said AT&T has asked the FCC to allow it to block calls to some of the same rural exchanges that Google Voice is blocking.

An AT&T spokesman said the carrier has never asked the FCC for permission to block calls to rural exchanges.