A there are no international restrictions on using facetime, since it runs over the internet, and not any particular carriers cellular network. If you are somewhere internationally roaming and you use facetime, itll use international data. If you have an apple device and so does the person you want to call, facetime is a voice and video calling app that you. Facetime is free when using wi-fi however will use your data allowance using. Are using facetime while abroad on a data connection this will be chargeable. However, if you are using facetime in overseas, the only charge or cost you incurred is the internet charge. If youre connecting to another apple user, you can use the built-in facetime app.
Again, much like whatsapp, facetime is absolutely free no matter what. You may incur data charges if you use it without wifi, but you will never. You could enable airplane or flight mode and then manually enable wifi. That should prevent the phone from connecting to the cellular networks. Pretty much everyone is on whatsapp nowadays and, unlike facetime, its available to apple and android users alike. .