Well, you do not tell us any of your ports or even what part of the world but we can still give you an answer. Assuming you are talking about Europe you can buy calling cards in any country, usually in tobacco stores. Some of the cards are only for a specific country and there are others that will work in any country (you dial a toll free number and use a code). Also keep in mind you can go to many US stores and buy a calling card issued by companies such as ATT that will work in any country. Or course the major problem is finding pay phones (everyone in Europe has a cell phone) but there are usually some pay phones at the ports and also in post offices.