There are alot of VoIP apps but some of them are easy to use, work great (sound is more then clear) and have very cheap plans for international calls.
One of this app is Vox Mobile for Android. Vox offer 2 type of services:
- one is pay as you call – no monthly plan, call anyone just when you need it
- monthly plan – free voice mail and a real telephone number
Another great feature is free video and voice calls in the Vox network and 60 minutes free International calls.
In the time I write this article Vox Mobile was already downloaded by more then 100 000 times just in Google Play and from 5 start have a score of 4.4 given by a total of 950 happy users. As a app developer myself I know that with 950 good reviews you hit the top.