I-Vitta Sim is good for calling from Europe and Internet in other continents.
You can use I-Vitta Internet almost everywhere in the world, and data charges are less compared to other world roaming sim cards.
You may install a firewall on your mobile and allow only the apps you required like-Whatsapp ,Actionvoip , Nymgo etc.
Also switch off media download from whatsapp Settings.
If only whatsapp is used, using 1 Mb( ie 15 cents ) – you may send hundreds of text messages.
Calling through voip is also cheap- in 1Mb , you can speak for approx. 5 minutes.