I’m travelling to Japan

JaneBOOT_468078 Providing that you have a reasonably modern phone, then Esim is the way unless you want to buy a local sim in Japan. You may also need to consider how much data you are likely to use in the time there.

I have found Roamless to be very effective. They are not always the very cheapest for data. You load your account with credit and then can use it in loads of countries. They tell you the rate in each country and your credit is then gradually used up to pay for it. If you have credit left over, it stays on your account for another time

Simple example: -  Buy credit - use Esim in Australia - credit left over and stays on account - months later in Switzerland (not EU) and use credit for data there.

There are other companies and some will offer fixed data for a fixed period in rest of the world.

I will state now that I have no link to Roamless but just found it very useful