Traveling overseas, I decided to wait a day or two to get a local sim card. To my surprise, I was receiving phone calls from NZ numbers. To avoid any costs, I switched to Airplane mode (and leaving my phone on pointless) until I switched sim cards.
I know you're able to turn off data roaming but is there a way to just switch off global roaming? Global roaming (at least with Vodafone) just isn't an option for me and I like being able to use wifi until I'm able to switch to local sim cards when I'm overseas.