WhatsApp’s massive growth—and astounding acquisition price—had a lot to do with how the app made texting free from one country to another. Now Boston startup Flyp is aiming to follow a similar growth path by doing the same for voice calls.

This past spring the company introduced their app for easily setting up multiple phone lines on their smartphones. It’s also pretty cheap—the first additional line is free and the second additional line is $2.99/month.

Today, Flyp is debuting a new service that lets its app users make calls and texts for free between the U.S. and 15 countries in Europe. The service works by transforming all Flyp communications into local calls—i.e., the number will show up as a local number—so that they’re covered by the customer’s wireless plan. And only one party needs to have the app for the calls between countries to be free.

“The phone app and the phone experience hasn’t changed in 20 years,” Flyp CEO Peter Rinfret said in an interview. “We’re really about changing this entire experience and going down this whole disruption line.”

Rinfret said the approach offers higher-quality and cheaper calls to other countries than current options such as Skype, and also better quality than WhatsApp, which has added voice calling. Countries covered now include the United Kingdom, Austria, Belgium, Denmark, Finland, France, Germany, Ireland, Italy, Netherlands, Norway, Portugal, Spain, Sweden and Switzerland, along with the USA. Canada will be rolled out the week of Nov. 16, and Flyp plans to make an additional 20 countries, in Eastern Europe and the Middle East, available by the end of the year.

Flyp says the service for calling other countries will differ a bit from the within-U.S. calling service. Users who want to call other countries can get one line for free for 90 days (which can be extended if users share the app with others). Otherwise, the lines for calling other countries will run $2.99/month. Making calls within the U.S. on the first line will remain totally free, Rinfret said.

Flyp has a staff of 22 based in the Back Bay, and this month opened a one-person office in London. The company has raised funding from investors including Boston and West Coast venture capital firms, though the specifics aren’t being disclosed for now, Rinfret said.

Flyp’s service works through the use of proprietary telecommunications technology that’s housed in the Boston area and the West Coast—middleware that controls the calls and switches that connect the calls to their destination.