[kungtotte]

The amount of roaming you get depends on your carrier and contract. We get up to 20 GB of roaming or your contract data cap, whichever is lowest. E.g. me and my wife can roam for 20 GB because our contract is for 24 GB, but if we had a 12 or 6 GB plan we could only get 12 or 6 respectively.

[jahnu]

Right. That's why I said needlessly complicated :) Takes so much effort to work everything out. They rely on this to make profits from mistakes.

[Someone]

That is much harder now; they now have to warn you when you reach your limit. See question 17 on https://ec.europa.eu/digital-single-market/en/faq/frequently...: "Therefore, as long as your operator has not contacted you while abroad, you can roam like at home without any worries."

So, they still can charge lots to those who, getting warned, don't immediately stop using their phone.

It is complicated because this is a political compromise. Everybody knows where the EU wants to end up (the frequent use of 'may' in that answer is a nice indicator), but that means shifting income of operators around (in general, operators in popular holiday countries lose a substantial source of income), so it can't happen in a Big Bang operation.