I don't know what country you're from, but in most of Europe and the US (or anywhere infact!) why would you not have a data plan for your phone? It's quite difficult to find a phone plan without some form of data included, even PAYG, and the price difference is often negligible.

Fair enough if using a fashionably retro 'dumb' phone and not a smart phone, in which case you can't use WhatsApp anyway. If you are using a smart phone without a data connection, then why? Surely you're missing out on all of the benefits of owning a smart phone like maps and instant access to online information, free messaging (WhatsApp anyone?).

If you just don't want a data plan, you can still use WiFi which would likely cover you for 80% of the time (home and work).