Yahoo plans to activate Internet phone capabilities for Yahoo Messenger users in the U.S., a little more than three months after announcing this feature. The upgrade to the instant messaging service, called Yahoo Messenger with Voice, lets users dial out from the IM interface to traditional or mobile phones. Yahoo Messenger users are also able to rent one or more phone numbers from Yahoo to receive phone calls through the IM interface. Calls made to phone numbers in the U.S. and 30 other countries with heavy telecommunications traffic will cost 2 cents per minute or less.