Beware of real looking invoices (they call it a statement, but they know that means invoice to you) from DNS Services, or anyone else making this claim, in the mail that appear to be for back up services, or any web related services, that you don't recognize.
Red flag #1: What keyed me into the scam was the nameservers 3 and 4, it seems they pull as much information from the domain's WHOIS listing and then add what looks like their supposed namservers to the record they send you. So you are supposed to say, "Oh, I must have signed up for that without knowing it and since it shows me right here I have been receiving the service, I guess I better pay for it." This scam has shown up from west to east coast, ignore it and they will be out the $0.45 in postage.
What is scary is that they have a very legitimate looking website, so I checked it out to see if the website listed on the invoice was an innocent victim of this mail in scam, but the same phone number and address is listed on the website too. So it appears they offer some kind of service, but they are hoping that you do not notice the inactive next to their nameservers that magically got on your WHOIS record according to their "statement".
Red Flag #2: They also have included an "this is a solicitation...." disclaimer mixed in with other text many are sure to miss to cover their asses.
Red Flag #3: What I am left thinking is how will they gain access to your domain without your consent, so do they offer a real service?