There's indeed all kind of commercial issues. No-one will disagree on that.
Yet, daily practices are very strange pricing schemes with all EU telco's. Where calling mobile may be cheaper than land line. But roaming is indeed a very practical issue for anyone crossing a border, and getting charged over 2 euro for 1 megabyte of data is more the rule than the exception.
Smarter users avoid getting unexpected bills using pre-pay plans. But on average, _everyone_ is being ripped of left or right. There are no fair plans. It's hard to find a,say, 100 euro true unlimited plan. It's hard to find roaming at normal prices. It _does_ exist though, it you search. But as said, most providers will just rip you off whenever they find a chance.
It is interesting to see how the EU and USA mobile markets evolved differently, which I attribute in part to the different cultural identity in the two places. US Companies see themselevs as US companies and so it was natural for them to dvelop a US network acrosss the entire country. The EU companies were more likly to seethemselves as French or German as were regulators in those countries who would protrct them from foriegn competition. As aresultyou have a very localized network rather than an EU wide network.
More legally - this shows how the EU has sometimes embarrassing little power. The EU parliament votes. The joining countries overrule. They just use 'EU' as excuse when convenient, and ignore as soon they please too, which often leads to schizophrenic state politics. This is just a symptom.
Concluding: the EU parliament chooses the most ethical-correct choice. The members of the EU choose to ignore it for, mostly, commercial reasons.
The EU is learning ehat the US learned right after the American War. A confederation does not work to create a single political or social entity.