If all your friends use WhatsApp/Messenger sure that works. However if you have friends in China you need WeChat, in some places Line is the main platform. Some people tend to use Google Hangouts or FaceTime only . A lot of friends do not want use any FB products and will use Signal/Telegram etc
Even if SMS is expensive, email is still quite free. It works almost like SMS/messaging on phone, you get push notifications on your phone and you respond.
I move around about countries every few months, keeping a VOIP/Skype phone number as the number anyone can reach you at works for me, while my local number is more for getting an internet connection and occasionally for signups to local apps (like rideshares, food delivery etc) that reject some VoIP numbers .
