jaxtr.pngJaxtr, a service for dodging international calling fees using your phone, has raised $10 million in series A round led by August Capital.

It says it has doubled in size in the last month to a million users.

The Menlo Park, Calif. company (more detail from our past coverage here and here [update: first comment below]) allows you to make free phone calls over the web or your mobile and landline phones, including low local rates for international calls.

When you sign up and make your first call on the web, you get a unique Jaxtr phone number and web address, such as www.jaxtr.com/mattmarshall.

People who want to call you can simply click on the web address link and get directed to your current phone number, as you have it pre-selected on Jaxtr — without you having to reveal your real number.

The company also lets you embed its widget on web pages so you can make or receive calls, say, on your Myspace account; it also launched a Facebook app in late May, but it only has a little over 12,000 users three months later.

Jaxtr has between 70 and 80 percent of its total users making and receiving calls from mobile phones simply because a Jaxtr number can be entered into a mobile address book like any other number, chief executive Konstantin Guericke tells us.

While Skype, Jajah and other internet-based phone services also provide ways to make free international calls, Guericke says this alternative phone number is more convenient for mobile users because they don’t need to download a mobile application, like Skype, or access a web browser, like Jajah. It’s similar to GrandCentral, the company bought by Google, which provides a single number you can use anywhere — although it gives you a single URL instead.

Eighty percent of total Jaxtr users live in 220 countries outside of the US, although Guericke says US users are three times as active, overall.

More than 16,000 users are now registering per day, the company says, with nearly three quarters of users in their 20’s.

Jaxtr was almost acquired recently, Dave Hornik of August Capital tells us — from another private company headed to an IPO (but not Facebook), he says.

While the offer would have been a good return for Jaxtr and its investors, Guericke says Jaxtr took the funding to try to replace the multi-billion dollar industry of selling calling cards with minutes for making international calls.

Jaxtr plans to make money by charging people who use more than their allotted 100 minutes per month; he hopes to get 20 million users in the next twelve months and is planning for only around one percent of these users to pay for additional minutes.

Other returning investors include the Mayfield Fund, The Founder’s Fund and three early Skype backers: Draper Richards, Draper Fisher Jurvetson and Mangrove Capital.

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