Just saw this on another forum. Free Whatsapp use around the world with no catch!
All you have to do is buy their $9.99 SIM card, install the official Knowroaming IOS/Android app, and you can make unlimited Whatsapp messages/calls everywhere
I have ordered a few SIM cards to try out the service, so far I have not encountered any big issues other than having to manually update the APN (It is not difficult if you pay attention to the user guide)
Here are voucher codes gathered in this thread, seems most offer 30% Off purchase of SIM card + additional free $5 credit / FB/Twitter $5 bonus.
*Update (June 14th 2017)
Free Whatsapp data/calls are still functional as of today.
- Unlimited Data now in 100+ countries
Get 1-Day Unlimited Data FREE with purchase
Use code DATA100 (good until June 15 2017)