It's better to do a local call before you go overseas. In my recent experience, too busy and forgot to call MBB. No issue to swipe and pay overseas. However, within 5 minutes, my phone rings and CS asked if I'm at XX shop at YY city. So, you will get charged for roaming.

Of course, if you don't pickup, your next swipe maybe blocked till CS can contact you.

You mean me ?

I prefer to take the effort to call the CC banks after immigration or while at boarding gate, normally will have spare time there and I make it a habit.
If I don't answer bank calls while overseas, I'm afraid my subsequent transaction overseas maybe rejected, and I don't want that trouble. I've seen several times my foreign colleagues panicking and start calling their banks (international roaming calls) while check out hotel, and need to rush travel to airport/etc.

Also, I got call at 3-4am local time before cause I use it many hours earlier to check-in deposit into hotel in US continent, while it is midnight in Malaysia then. disturb my sleep and rest for important work meeting the next day.