Free Calling using Iphone or Android.

Iphone and Android phones ssupport loads of applications that allow you to make free phone to phone calls 

Applications that support free phone to phone calls :

Skype:

Skype is world’s most popular PC to PC telephony service with more than 350 million users across the globe. 

Download skype for your phone here :

http://www.skype.com/intl/en-us/get-skype/on-your-mobile/download/
for more android trick visit www.androidxplore.com
Viber :

Viber is a mobile calling service that works on mobile phones with wifi & 3g internet. Viber not only supports free calling but also supports free text messaging to other viber users.

Download Viber for your phone here :

http://www.viber.com/