When using your mobile phone keep in mind that only digital phones with GSM subscriptions and a roaming agreement will work on the island of Ireland
If you’re not sure what type of phone you have, check with your supplier before you travel. Almost all EU mobile phone networks will have a partner service in Ireland. Be sure to check what roaming charges are for both call and internet tariffs as these can vary.
The EU Parliament has set new maximum charges for mobile phone usage throughout Europe. There is a cap on the amount that can be charged for downloading data while abroad (70 cents per MB), and companies must alert customers when they approach €50 in data usage.
Companies such as SIM Local offer local SIM cards to visitors coming to, or already in Ireland. The card is inserted into the phone, pre-loaded with a certain amount of credit allowing you to readily avail of internet access and phone calls at local tariffs.
Pre-paid phone cards are available both in the Republic and Northern Ireland and are convenient and easy to use. Cards can be bought from newsagents and some post offices. Coin and credit card-operated pay phones are available in some places, but are generally confined to urban areas and larger towns.
If calling Northern Ireland from abroad, all telephone numbers must be prefixed with 0044 (drop the first 0 of the local code. For example, for the local number 028 123 4567, a visitor would need to dial 00 44 28 123 4567 on a foreign phone.) If calling Northern Ireland from the Republic of Ireland, replace the prefix code 028 with the code 048.
If calling the Republic of Ireland from abroad all telephone numbers must be prefixed with 00 353 (drop the first 0 of the local code. For example, the local number 01 344 1111 would need to be dialed as 00353 1 344 1111 from a foreign phone).