We often suggest to those how are going overseas that WhatsApp over WiFi is a cheap and convenient way to keep in touch with acquaintances at home. This is a useful guide as to how to set up and to get the best out of of WhatsApp :-
How To Use Whatsapp: A Guide For Seniors - Talk Android
https://www.talkandroid.com/430580-how-to-use-whatsapp/
Although the guide seems to be aimed at older people, I believe that it could be quite useful to potential users of any age. 👍
