Can I demand cash for the laptop and how can I force them to refund the extension payments?

In April of 2008, I pawned a laptop computer valued at approximately $1000. I paid the extension fee every month until February 2014 when the pawnbroker refused payment to extend. I was told the item was sold in November 2010; however, I continued to make payments every month not being aware the laptop I pledged was gone. The pawn shop never informed me the item was gone and I was told that I defaulted on the loan so they had the right to sell it. They said their computer system has a glitch and that is why I was able to continue making extension payments. First they offered to replace my laptop with a less comparable one. I requested a refund of the loan extension payments and the manager stated he doubts that is going to happen. They refuse to give me a full refund of all payments made even though I have receipts for most of the payments. The last receipt is proof that that I made all the payments, but I provided additional evidence of payments made since 2008. Due to my health issues and my financial debt, I would prefer to receive cash to replace the laptop rather than another laptop.