Yeah - i also get calls about franking ink, which i unfortunatly fell foul of once - our machine doesnt use ink in bottles... and i got a box of 12 bottles.
I take calls for all types of office equipment, IT - hardware and software, Stationery ect.... I just tell the caller sorry not interested as we have recently taken out a twelve month contract for product service XYZ. It seems to do the trick, i also dont take calls from people who ask for the Stationery buyer, IT Buyer ect. who ever takes the call tells the caller that Mrs Diana Prince is responsible for that area of the business but she's on holiday/trainging/away from the office for long periods of time..... She's a fictional employee but it makes us laugh when she gets mail or calls....

)