Endless hassle to get a correct invoice

Requested an invoice for a computer that we purchased. The invoice had no company name, address or telephone number. It also indicated that we bought 2 computers, but we only bought one computer! We could therefore not provide our insurance company with proof of whom the computer was purchased, and what we paid for the computer. Are these computers 'grey' products or even ****** goods? Who is the seller?? When we finally did receive an invoice with seller details, the invoice still reflected that 2 computers had been bought! We bought ONE! Why Take-a-Lot get this right??