But in practice you may retain (and pay for) your subscription in the country of origin and should be able to use it within the EEA at no additional cost.
Though carriers tend to frown on this, and will state that this is not fair use, I suspect that anything outside of heavy or constant usage is unlikely to make them notice (I used a UK# in France for years before I initiated the cancellation; no word from them about anything)
oblomov