Hello
Please go to Settings >Apps >Downloaded tab and touch Whatsapp > Touch Uninstall > Touch ok.
If you still see the whatsapp icon even after uninstallation' note that it is just a whatsapp downloader and it has been made a system app' you will need to root your AG selfie in order to be able to uninstall system apps. See how to root your phone here http://www.satechhelp.co.za/10112/Root-Ag-Android-Phones You will comment below for further assistance.