If you were being hit with this as a private individual so consumer protection laws would apply, I wouldn't fancy their chances at all, but if I've inferred your situation correctly that's not the case here? I'm afraid EU law is often very bad at protecting small businesses, so while I wish you luck in fighting the good fight, I wouldn't be so confident about your legal position as a corporate entity. But of course, take proper legal advice, as it looks like you are. And maybe Irish national law can help you even if the European provisions don't.

Hang on, does this mean they are making you call at international call rates?!?