That's literally the reason I even heard of or installed WhatsApp a few years ago. I was spending time doing work with my church in el Salvador and a bunch of the locals there used WhatsApp because it avoided the insane SMS fees the telco charged. I installed it just to chat with them internationally.
Now almost all my friends are on it and it's great. I love the cross-platform ease of use, E2E encryption, and easy web interface. I'm just scared of how Facebook will ruin it.