There are a couple of way to get in contact (in English) with TCDD Tasimacilik which operates all passenger trains in Turkey are as below:

Call center: +90 444 82 33

You can get information about train services and buy/change/refund tickets for the trains that have online sales.

WhatsApp: +90 507 321 82 33

Staff gives information or help about problems. No tickets sales here.

Mail: cozum@tcddtasimacilik.gov.tr 

You can send your requests and complaints about trains.