How can I contact a bugged website to cancel my plan?

[Minis]

This website is so fuc**** bugged. I'm trying to contact help centre and they ask for a "Valid email and name" to be able to contact them, but when I check it everything is OK!! Wtf!! And there is no telephone number, no contact email anywhere. What a disaster, I'm moving to IONOS: better service with phone and email quick reply, cheaper and more intuitive.

Anyone can give me some info to contact them? Their Web is a bugged disaster and I want to cancel my plan