I've had contact with ÖBB customer service a few times and did get responses. Including reimbursement of fares that were too high and payment of compensation for delay.
How did you contact them? Did you use one of their online forms? That's what I did.
They're required to reply within one month, or send a holding reply and then the final reply within 3 months. Compensation for delay must be paid within one month. All per EU regulation.
If you're having trouble getting a response, you can contact the national enforcement body:
https://www.apf.gv.at/en/agency-for-passenger-rights.html
Direct link to file a complaint there:
https://www.apf.gv.at/en/passengercomplaints.html
Yes I used the online form. Sounds like they are good when you can get to them. My last message was 13 days ago, which seems like a reasonable amount of time to me to reply, but I’ll keep waiting.