Trying to book a room at the Parkhotel Mondschein. link

Looking to book 3 adults in a junior suite, but the property only shows availability if I select 2 adults, even though all of the suites say up to 3 adults can be accommodated. E-mailed my concierge and she says I need to call the globalist line due to having the take the credit card security code over the phone. I called the globalist line and they said I have to book a Mr and Mrs Smith property on the website.

What exactly am I supposed to do? I guess I'll e-mail them and see if I can just book for 2 and make sure they know it's actually for 3 and that I need an extra bed.