The Blue Button...send us a message..????

Good day Partners.

I am getting very frustrated trying to send booking.com a message. my problem is that I wish to change the way I pay my invoices. I am being lead to the financial overview page & asked to press the blue button to send a message.."The blue button" doesn't seem to be working as it takes me to a page that says I have no message...??? Does anyone know how to send a message to them as I cannot reply to any of the emails I've received...Please HELP...