Phone cards can be purchased from small shops in every city, as well as street vendors that sell magazines and cigarettes.  The phone cards are very easy to use, and local people will assist visitors if the card doesn't explain the instructions easily enough.

The best way to use a phone card is from a Greek payphone, landline or from a Greek mobile - purchase a pay-as-you-go SIM on any Greek network for about €5 plus credit in a local mobile store (you will need ID to register it).

If the calling card access number starts with an 8 (eg. 807 xxxx) then it is a free phone number, so wont cost anything ifcalled from a payphone or landline. These numbers cannot be called from mobiles however.

For cheap calls from mobiles, make sure you purchase a calling card that has a local access number (such as an Athens number starting 211).

Calling cards are typically available in increments of €5.