KFC Bedford poor service

Used the newly introduced delivery app at the Bedford view store. Ordered 6 colonel burgers. Only received 2 on delivery. Tried repeatedly to get a hold of the store but with no success. Contacted head office - they too could not get in touch with the store. One of the two burgers delivered had a blue foreign object on the pattie which was clearly visible. To date KFC has not taken any steps to rectify. Considering doing a chargeback with my bank as kfc not interested in rectifying the mistake. KFC head office ignores all emails.