Why Is The Roaming Free?

[Effendi]

It could be free also for Manx Telecom if they wanted so. But all "normal" carriers make us pay everywhere, so does Manx too, it's just a non-written agreement among all the mobile operators.
I suppose that small countries like IoM or FL can have quite big advantages in terms of interconnection fees, so they can manage to have free calls in many countries for their users and still getting money with interconnection.