Cold called one of our locations, claiming they we...

Cold called one of our locations, claiming they were the manufacturer of our receipt paper. Knew the manager's name, printer models, etc. Claimed they were switching the paper due to customer complaints. Sent us an invoice for 18 rolls of paper @ $10.95, plus shipping and handling. We normally pay our regular vendor $1.70 per roll, plus shipping and handling. I refuse to pay shipping to send it back; will not pay the bill unless someone puts a gun to my head.