Check whether you have an active spend-cap, which would prevent additional charges being incurred. In the Republic of Ireland you are roaming on Irish networks, calls within Europe should be included but is worth ruling out.
https://ee.co.uk/help/mobile/manage-use/pay-monthly/set-up-and-manage-spend-cap
Otherwise, what happens when you try calling this number? And is it the same behaviour on all the Irish networks?
