Like everyone else here, the company I work for also received a fake invoice from this so-called company. I handle all incoming invoices and didn't recognize this company or service. Neither did our IT people. No one from our company sought them out or requested their service.
As mentioned by other reviewers, there is a section in fine print on the back that states "Sign up date is considered the date WebsiteBackup receives your payment."
So don't pay it! This is not a real invoice!