There have been numerous reports about problems with messages from this app.  I have to wonder where people are getting it and whether it has been vetted.  I would delete the app from my phone if I were you and run a scan to see if it installed any malware or other nasty things.

I have been seeing a lot of reports of misdeeds because of an app called WhatsApp. According to the web site they are located in Silicon Valley, there is no physical address on the contact page, and the web site itself seems sparse considering what it is and who put it up. I think the app is either malware, or possible has been taken over by criminals. Either way is is a serious threat to the unwary.
What I have so far:
Company web site: http://www.whatsapp.com/
BBB Page from Silicon Valley brings up this F rated company from Texas? and nothing else?: http://www.bbb.org/houston/business-reviews/m ... lle-tx-90031535
Google map of that Texas Address and a web search shows a bunch of restaurants: https://www.google.com/maps/@25.959585,-97.53 ... NQt5se7QwgQ!2e0
Bizapedia search brings up this: http://www.bizapedia.com/ca/WHATSAPP-INC.html
Which seems to be maybe a shopping center?: https://www.google.com/maps/@37.337857,-121.9 ... w2riCKGgPFA!2e0
Yahoo also brings up two more companies at that address, a Postal something store and this company: http://www.bizapedia.com/nv/ROSE-ARBOR-GARDEN-LLC.html
So my guess is that the address is a drop box. Also, the businesses have different owners and registered agents.

A web search of whatsapp scam brings up a multitude of reports on this app being used to transmit malware and viruses to smart phones to capture information and passwords.