Gardai would advise people that returning calls to unknown numbers can be costly and ask people to exercise caution when they receive a missed call from such numbers. Be wary of multiple calls/missed calls being received from the same number that you are unfamiliar with – they could be trying to engage you.
Do not call back any number that you don’t recognise. If you dial back an unknown number by mistake, hang up immediately on calls where there appears to be no recipient on the other end or where you are left on hold as it could cost you money.
If you have friends or relatives abroad that may be calling you, store their number in your phone so you know its them.
Most phones have the capability of allowing you to block a nuisance number from contacting you.
Do not provide any personal information, for example, banking details/PPS number/credit card details/name and address/passport numbers etc. No institution will ask for these details over the phone.
Unfortunately there is no way to identify a scam call number immediately and they can resemble a very normal, familiar, geographical or international number. Google the number and it may tell you its origin.