Calls over MyRepublic's trial 4G mobile network have to be made using its MyVoice app, which is now in beta release.
The app, which works like Skype, allows users to call other MyVoice users as well as non-users.
But unlike Skype, MyVoice users get an eight- digit mobile number.
MyVoice-to-MyVoice calls are made over the mobile Internet, thus tapping credits in the existing unlimited data bundle.
Calls to non-users of MyVoice - mobile or landline users of other telcos - are partly routed over the traditional telco network. Such calls would incur a charge of 2 cents a minute for local calls, and charges from 6 cents a minute for overseas calls to the United States, Britain, China and Hong Kong.
Trial users are given a $10 call credit on MyVoice for both local and overseas calls.
Should the company get the fourth telco licence here, it said it will set up capabilities to let consumers make calls in the traditional way without using the MyVoice app. But call rates will be cheaper via MyVoice, its spokesman said. Pricing details are not available.