Vietnam travel using Westpac Worldwide Wallet

Howdy I’m backpacking Vietnam for 3 months and have a possibly stupid question. SE Asia is mostly cash but I’ll be using mobile banking for rides and online bookings and such. I’ve opened a Westpac Worldwide Wallet account and have the travel cards. There’s no option to transfer AUD to Vietnamese Dong. Am I going to be able to withdraw cash from banks or ATMs using this card if there’s no VND on it, or will I just receive a high fee?