I'm in Greece and will be in Thessaloniki in a few days. I plan to take the bus to Kastraki where I have a 3 night stay to see Meteora. I've searched online and on this forum, but I'm unable to find out how to buy a bus ticket. I don't want to rent a car, as I'm going on to Corfu and would rather not drive the mountain roads. At this point it seems best to just go to the bus station in Thessaloniki when I arrive, unless anyone here has information that can help me.
There is no direct public bus line from Thessaloniki to Kastraki.
You will need to take a KTEL bus to Trikala (journey time: 3h) from the Thessaloniki bus station located here:
https://maps.app.goo.gl/ftw3RXDKyGA9SjBK9
Then, at Trikala bus station, you'll need to take another bus to Kalambaka (journey time: 30 minutes).
Information and tickets are available here:
I am traveling on this route in September. I researched the buses and came across the same website for ticket purchase that JoLui included in her response (via https://ktelmacedonia.gr/en/routes/tid=34). You can buy a ticket to Kalambaka from Thessaloniki using that link, but you will be changing buses in Trikala.
Thank you both for your responses. This is extremely helpful. :)