The FCC is expected to look into how Google (NSDQ: GOOG) operates its voice-calling service and whether it elects to restrict some calls, reports the WSJ, which quotes people familiar with the situation. The inquiry is expected to be sent later today.

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Late last month, AT&T sent a letter to the FCC asking the agency to consider regulating services, like Google’s Voice, which uses the internet to send and receive phone calls, rather than traditional wired infrastructure. At that time AT&T (NYSE: T) accused Google of blocking calls to some areas, where the rates can be more expensive. Later, Google wrote on its web site that in some cases it does block calls, but argued that it was OK because it Google Voice is free and it doesn’t fully replace traditional services because it requires a broadband connection or phone in order to use it.