imo has updated their mobile app for Apple iOS devices.

Users of imo on iOS devices can now make voice calls using the app.

It would work with other imo users on iOS and Android devices.

The company said:

imo v3.2 is now available in the App Store! The update includes a new voice calling feature allowing you to make calls with friends using the imo iPhone or Android app. To make calls on your iPhone, tap the phone icon next to your contact’s name and wait for them to answer.