All Universities provide internet access to their students, in their informatics labs. Usually they also provide Wi-Fi access as well, to classrooms, common areas and dormitories.
Internet access is widely available in Greece. Most hotels and public places, like restaurants, coffee houses, etc. usually provide free internet. Sometimes you may need to ask the waiter for the Wi-Fi password. In addition, there are many internet cafes, charging at relatively low prices.
Internet cafes and cafeterias with free WiFi can be easily found in almost all cities across Greece. The connections are usually very fast and the prices are very reasonable, ranging from 2-4 euros per hour. Most internet cafes exist in the busiest parts of the town and offer both wireless connection and desktop computers. This way you can sit at your table with your own laptop and connect via WiFi, or you can use one of the existing computers.
Using pre-paid calling cards is the cheapest way to make international calls (45 minutes cost approximately 1 euro). You can buy them from many shops and kiosks (ask for an international calling card) and use them from a land line anywhere, including public phone boxes.
Regarding mobile telephony, Greece uses the same GSM system as most EU countries, Asia and Australia. You should have in mind that USA and Japan use a cellular phone system that is incompatible with the European.
Post Offices are open Monday to Friday 07:30 – 14:30 and closed weekends and holidays.
In Athens, there are three post offices are open beyond regular hours: