Cannot unsubscribe

When I try to unsubscribe from Cheapo Air's email list, their site tells me that my email address is invalid.  This makes no sense to me.  I typed my address in AND I even copy and pasted the address in, but I still could not get  Cheapo Air to recognize it.  If they don't have my email address on file, then WHY ARE THEY SENDING ME SO MANY EMAILS?  When you go to their customer support page, they only give you options to discuss new travel arrangements or existing ones.  They have no options for complaints like mine.  Cheapo Air's website is completely useless unless your issue involves something that will make them money it seems.  If they do not stop sending emails I will change my address and make sure no one I know uses them again.  There are too many options out there to continue to use an incompetent service provider.