The sound clarity was good when I used Nanu for the first time, but later it changed from good to worst. Also, getting free credits is next to impossible which makes it a worthless app. Whenever I got an update notification, I thought this time the problem had been sort out but not. I always encountered breaking voices while making calls and sometimes not even that, completely voiceless. This app is not at all suitable for making calls. I do not recomend this kind of apps to anyone.