EXPIRED VOUCHERS IN PROMO PACKS

We purchased Whiskas Promo packs in February 2019. At time of payment we wanted to use the vouchers only to find out that they were EXPIRED in December 2018. Manager on duty took the vouchers to the value of R 1800.0 and assured us he will get Whiskas HO to contact us. 5 months passed and no contact was made until we went to the store.When we approached the manager he said he will get Whiskas to contact us. 1 week passed and they did, however store is now disputing the voucher values and requesting proof of purchase after 5 months of no contact. Store refuses to reimburse as well as Whiskas. we had made purchase from 2 stores , HYPERMARKET DURBAN NORTH and PNP SPRINGFIELD, both stores has EXPIRED products on their shelves.