Geektastic: If you use a local SIM, how can people call you? Doesn't it effectively mean your number is off line until you get home?
Not everyone uses their devices for that. People can still get me on wechat, facebook messenger, twitter, ICQ, sometimes skype, email, instagram, snapchat, and probably a few others I have forgotten about. None are tied to a number that is used by a telco to identify me to their billing system.