Also note it applied to roaming within the EU. You’re still in their clutches if you go further afield.
Rationale was that treating people from one EU country differently than from another was against the union. Imagine paying inter-state roaming in the US.
The new UK system makes no sense. My current mobile provider (O2) will offer me unlimited data usage in the USA but will charge several pounds a day extra to use my phone in France.
Companies will charge what they're allowed until either the market forces them to behave, or failing that, the government.
