You can purchase it via:
a. MyDigi app - before or after arrival at destination country
Step 1: Login to the MyDigi app.
Step 2: Click ‘Buy Add-Ons’.
Step 3: Click ‘Roaming’ and select the country/region.
Step 4: Click on the roaming pass you intend to purchase.
Step 5: Select and confirm the date to activate the roaming pass.
Step 6: Click ‘Confirm’.
Note: Ensure you’re connected to the internet eg. Wi-Fi
Or if you don't have internet connection, you may purchase it via:
b. UMB by dialling *800# after arriving at the destination country.