WhatsApp, the startup recently purchased by Facebook for a cool $16 billion, is looking to add voice calling in the near future, a prospect that is likely making phone companies even more nervous.

Comprising 450 million users, WhatsApp is the largest mobile messaging service worldwide. The Silicon Valley startup announced Monday at the Mobile World Congress in Barcelona that WhatsApp voice messaging will launch soon, PCMag.com reported via Reuters.

The service essentially offers text messaging without the restrictions that come with texting through a carrier.

"We are driven by the mission that people should be able to stay in touch anywhere and affordably," CEO Jan Koum told audiences, as reported by Reuters.

WhatsApp, which will continue to operate as a separate company even after the Facebook purchase, already lets users leave voicemails by pressing and holding a microphone icon above the keyboard, according to PCMag.

The upcoming voice calling service will start with Android and iPhone operating systems and then expand to Blackberry and Windows phones, CNET reported.

Koum said the new voice service would function more like a telephone call and seemed confident that the venture will find success.

"We think we have the best voice product out there," Koum said, as reported by CNET. "We use the least amount of bandwidth and optimize the hell out of it."

He said that WhatsApp will be operated in a fashion similar to Instagram, which Facebook purchased for $1 billion in 2012.

"In order for WhatsApp to be successful, it really needs to be independent," Koum said. "There are no planned changes. We can only get our product to a billion or 2 billion users if we continue down the path we started on."

The company may need to strengthen its servers since a boost in popularity caused WhatsApp to suffer an outage over the weekend, according to PCMag.

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