It's included in all memberships.
Some info here:
Free whatsApp FAQ
and here
http://www.48months.ie/membership-plans
WhatsApp messaging is only available if you have data included (i.e. in your membership plan or if you buy a data add on). You will not be charged for data when you use the WhatsApp messaging service for messages via the app but if you use the voice features on WhatsApp you will incur data charges.
One thing that doesn't seem to be mentioned and is I believe a condition of this offer is that it only works as long as you have not used up your data allowance. My understanding is that once you have used up your data allowance it no longer works until you buy a data add-on. But I'm open to correction on that if anybody knows better...
What do you mean by "data roaming"?
Do you mean data while roaming abroad?
If so then that won't work as 48 don't support data services while roaming abroad and you can only access internet services via wifi where available.
Hope this helps.
