Best data roaming for Vietnam and Cambodia

[MariaKirwan]

I will be travelling in Vietnam and Cambodia for 3 weeks and wondering about best approach for roaming costs. I have a UK monthly contract and would like to be able to take calls (usually on WhatsApp) and use internet and some apps 

[bristolian]

Your UK allowances will not be usable in Vietnam or Cambodia, the charges are set out at https://ee.co.uk/help/help-new/roaming-costs - WhatsApp is an internet-app, so usage of it will just be data usage like any other app.

If you're PAYG, roaming is auto-enabled when your phone is first used in the UK. Pay-monthly users should text ROAMING to 150 to ensure coverage abroad.

[XRaySpeX]

You'll receive a msg on arrival in a country offering data add-ons. They will be expensive & small (in MBs).