[andor]

I thought these rates were for legacy Multimedia Messages, not for Whatsapp traffic.

http://en.wikipedia.org/wiki/Multimedia_Messaging_Service

Edit: apparently not. The FAQ page states the SIM works only for Whatsapp, not for texts.

[MatthewWilkes]

It really feels to me that they're providing a mobile front end to whatsapp, not free connection to whatsapp. I guess it would route messages as texts and MMS.