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.
You can send your requests and complaints about trains.