There has been a recent resurgence of the so-called "phoner/toner" scams. They are popular because they are highly effective, very profitable and, while deeply unethical, not technically illegal (which makes them relatively safe scams from the criminal's point of view).
In this scam, you will get a very friendly call from someone who knows your name (possibly because they called your number late last night just to see whose name came up on the voicemail) and who may even claim to be from your own IT department. After a minute of friendly chatter, he/she will ask for the number on the printer behind you, perhaps saying that "it's part of our inventory of systems". The scammer is betting that most people today have a printer very close to their desks.
Several weeks later, you will receive an unsolicited replacement toner cartridge in the mail. You don't remember ordering toner but who keeps track of things like that? And if you didn't order it, one of your co-workers probably did. So you open the box and tuck the toner away for a rainy day.
Weeks after that, the scammer sends an invoice for five to ten times the market price for the toner cartridge. The scammer is counting on the fact that most finance departments will just pay small invoices and even if they don't, they'll forward the invoice to you for approval. You remember receiving the toner and, since most of us assume we are dealing with honest people, you are likely to approve the payment without checking the price. The great thing about this scam is that it's not illegal to charge too much for a product. Under US law, it's "buyer beware". If you agree to pay five times what something is worth, that's between you and the seller.
If you don't pay, expect a series of followups demanding payment. If you call about the invoice, the scammer will likely offer to play back a tape recording of your employee saying "yes" to a request for toner. The scammer likely did get your employee to say "yes" to something and then cut-and-pasted the sound clip in front of a different question.
If you get one of these scams, first refuse to answer the question. No one should be asking about your systems without cause - even something as seemingly innocuous as your printer models. Second, alert your Receiving folks to watch for toner or other office supplies coming from someone other than your regular supplier. If you can identify the shipment in time, refuse to accept delivery. Third, do not pay the scammer. Do not pay any return or restocking fees either. Under Federal Trade Commission rules, any unordered merchandise can be considered a gift. You didn't order it. You have no obligation to give them money. (You might, however, want to have your legal counsel send the scammer a cease-and-desist letter. You should probably also double-check your state laws. Ohio gives even stronger protection and permission to consider the unordered package a gift.)