ok, so how does this work?
when my SO was in new zealand I was using my old blackberry with a inactive MTN sim card and it worked... Using WLAN
my brother is on a top up contract, and when his airtime is finished, he cant call/txt but he can use whatsapp... no WLAN
if someone steals your phone, and toss your sim card and put in theirs, will they have access to your whatsapp and all your contacts