Ringo ... calls are routed through crystal-clear local phone networks – so there's no Internet connection required. And still, Ringo is consistently cheaper than digital competitors like Skype or Viber. Ringo has apps for iOS, Android, and Windows phones and is supported worldwide
Now Get 50 Free Calling Mins with Ringo Calling App. After that Ringo low cost calling app allow you to call any mobile or landline local/STD in India at rate of 19 p/min only. It lets you make lowest cost local and international calls without using the Internet (WiFi or 3G). Their prices are 25% lower than most other calling apps.