Expired goods

hi I purchased a tahini dressing on the 05.09.2014 at pnp strand square I got home and immediately started with supper after opening and starting using it I saw it has expired 30.09.2015 I took it back to the store with my slip and the manager Edward en Jenevieve blatently told me that product was not from that store. in my opinion he called me a **** because I walked out of the store with my slip and expired product with no refund or apology the product cost me R75.99. I am prepared to take a lie detector test to prove I am not lying Im disappointed and unhappy with his service and customer ithics. at this moment I do not know what to do or say as I am still in shock this was my first time purchasing this product and to get an old product from PIC N PAY is seriously alarming heaven knows how many old products they sell to their customers and we as customers do not check exp dates because you expect fresh products from a name like that thank you Natasha