I have heard from a few of my clients with questions regarding official-looking invoices that request payment in connection with a pending trademark application. As my office is identified as your attorney of record for trademark applications and registrations, and typically all correspondence is directed to my office, you should be highly skeptical about any such correspondence and make no payment. Whatever official registration services might be offered in such invitations, they are likely not connected to any governmental agency. Please forward any questionable documents/invoices to my attention by snail mail or email, whichever is easier for you.
Unfortunately, unscrupulous persons monitor applications at the USPTO, WIPO, and other governmental agencies and send official-looking invoices to applicants. Do not fall for this (or any other) dodgy request for payments.