JohnG don't say sensible things. P.S. they're not pretending - they actually don't know that the mobile networks did this long before the EU mooted it which is why the EU felt safe to do it in the first place. That plus the whole thing with them doing it with countries they are most definitely not required to would blow the average remainers tiny little mind.
Not for nothing but if they all reverted to the previous status quo they would in fact be a telco cartel and competition authorities would be forced to step in.
It isn't a cost it's a choice to charge and that's why people are so confused. The mobile networks already have enough stuff going against them, there's no reason to drive more people away.