Stratro Hosting – How to actually get in touch with support?

We are currently in the middle of assisting a client to move over to our hosting services, he has a few personal email hosting and a domain in Strato currently but we can't even update the DNS records or nameservers in Strato due to their basic control panel.

I've reached out to them by email but heard nothing back but I know they are part of IONOS and we need to get this resolved quickly since the client currently has no emails.

Has anyone had any success going through any other routes who have used Strato in the past? I just need to be able to speak to someone..