Where should I use the USIM when I travel to Europe?

I'm planning a trip to Europe.

I haven't decided exactly, but I'm going to look around Western Europe, not just one place.

For local USIM chips in Europe, which USIM should I use?

Do I have to buy and use a different one for each country?

Or can I use it in a way that I can use it all if I buy one because there is a global company?

826 2017-06-29 Gentleman

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