Staples Expired Rewards Cards, fraud University Park Florida

I moved and recently found 2 Rewards Cards.  When I presented them to the cashier, I was told that they were expired.  I talked to the manager and he told me that I must call the number on the back of the card.  After many tries, I could not be connected to a person.  I talked to the store manager again and was told that I could also enter my claim online.  There is no such way to recover my reward online.  I feel that I have been ripped off by $20 each card.  They are no longer my supplier.