Laptop pawned when rent was paid to extend. But laptop was sold

Posting on behalf of my uncle. He took his laptop to pawned it. Then near the expire date he took the papers and his id to only pay the rent to extend the month. When he whent to pay and collect the laptop at Cash Crusaders Brits they told him the laptop was not paid and was sold. He then queried with the papers and receipt that he paid the extension they relised they booked it to the wrong customer. Now they want my uncle to pay +/- R1450 then they will let him choose a laptop worth R3199. But his laptop was in perfect condition almost brand new well looked after acer laptop he purchesed it for R8499. And the laptops is not near the spec he had nor condition. Please can someone of head office management help to solve and help my uncle.