Hey - Have you tried the method here http://satechhelp.co.za/1611/Install-Whatspp-Messenger-Android-Without-Adding-Email?show=1611#q1611 - If you have already associated your Google/Gmail account with your Vodafone Smart Tab 3G, then you can try clearing cache and data from your Google Play Store app. Do this by navigating to Settings > Apps > All > Play Store > ...clear cache and data... from there. Then retry launching the Play Store app, accept the T&Cs, then retry downloading the Whatsapp Messenger app and observe. Let us know how all goes.