Pawnshop sold my item even when i paid the interest

I pawned my ipad4 64gb gadget i paid the interest to extend its maturity date. However when i went back to redeem my gadgt and settle the remaining balance,they informed me that the gadget has been sold. The manager wrote a note at the back of my receipt that 1month worth of interest will be waived until replacement is available.
Its been over 2months now and evrytime i call they inform me that they dont have the exact specs of the gadgt i had. They offered to replace me with the same model but with a lower memory 32mb provided i pay the same principal amount for redemption. And this offer is open until there is already an ipad4 32mb item that the owner failed to redeem. I dont think its fair on my end..do you? Please advise wher and to who i should ask for legalities for this problem.

Review your contract with the pawnshop. What are the terms and conditions stated therein regarding their right to sell the pawned item? What are the instances where they can legally sell the pawned item even without the owner's consent?

If possible, have the whole contract detailed out here so we can review how they do things and if they are indeed legal under the law.