accidentally got wrong domain cert?

I tried to get a domain certificate for "(mydomain)com". My ISP now tells me the PRIMARY needs to be for "www.(mydomain).com". How can I fix this? Your UI didn't allow me to change the primary/add-on. I've already paid for 2 years, so I just want to get through the process. How to do that? I cancelled the certificate, but now I can't get back to issuing a cert for the "www" version or anything else.