Have you ever received a letter in the mail pitching domain name listing services that looks very much like an invoice?
These companies promise to list your domain (website) on many websites for a sum of money. The thing that do not mention is that Google and other search engines do not use listings anymore; they organically find your websites and content, and rate SEO internally based on various algorithms. These domain listing services are scams. You should throw out these letters or emails and do not respond to them. Instead, do your research online and speak with friends/clients/customers/etc and hire a reputable web designer or web marketer to review your website content and build out posts with useful data that will improve your SEO scores.