TrainOSE has suspended quite a lot of its trains a year or 2 ago-they were (and still are) in dire financial straits-just as TCDD is. The main line Ath-Thess has been renovated and now has speedier trains, but east of Thess (toward the Türkiye) has only very few trains left and not over whole old line, but I dk till how far east. Very well possible that Alex.p has also lost its trains. Also the whole old network on the Peloponnesos is suspended.

If you come from TR its likely best to find a bus till at least THess-and think again if you really are so much train loving that you spend much more time and effort to find them and ride in. A railpass will only be worthwhile if you also plan to use it in many more countries. Also DO note that there are NO trains over borders at all to GR and also NOT Macedoni-RSerbije and aso NOT into Rep.Serbije-except to Cerna Gora. If coming from IST/TR the only-and then only in summer-train is the overnight to Sofia/BG with in high summer a car or 2 detached and going very slowly on to BUcuresti.