If you have any phone from these series Nokia Lumia 520, Nokia Lumia 620, Nokia Lumia 720, Nokia Lumia 920 you Can Download best Free Calls and Messages Application whats app for them , all of them run on Windows Phone Os from Microsoft Company.
Whatsapp is a free chat App supports most Nokia Phones , when you get verified with whatsapp you can make any free calls or send any messages to your registered friends on whatsapp service.
the first Year is completely Free then you must pay 0.99 $ Per Year ( Very Low Rate ) to use whatsapp service that will give you all features .
there are many people don’t know windows Phone Store which gives you thousands of free apps and games to your lumia phone .
WhatsApp Details :
Windows Phone Version : 7.5 and 8.0
Size: 5 MB
Website : http://www.whatsapp.com/
Whats New !!
* Fix crashes on Settings and app install on a small number of 7.x devices.
* Fix installation hangs for Finnish and Polish users.
* Address performance and stability issues when WhatsApp enters and leaves the foreground on WP8. We’ll continue to improve on this in our future updates.
* Some UI tweaks.