Debonairs Pizza
Rubbish tasting pizza - HALF A REFUND???

I ordered a large Tikka Chicken pizza from Debonairs Blue Route mall.
My 3 colleagues and I 'tucked into' the pizza but alas the disappointment was not far off.
The pizza smelled 'off' somehow and we couldn't be sure if it was the chicken on the pizza.
I called and spoke to the manager of this branch - Shaylinn who was kind enough to come and collect the pizza.
Shaylinn then explained that if something was 'off' on the pizza it could in all likelihood be the mushrooms as this is prepared in the morning.
Shaylinn took the pizza and after we declined her offer of another pizza was headed out the door with the half-eaten pizza and not a word regarding a refund.
When I asked her about getting my money back (for a product that was hardly suitable for consumption), she explained that since we'd eaten half the pizza, I'm only entitled to half my money back???
REALLY??? I was not aware this was Debonairs' company policy...
And... AFTER SHAYLINN CONCEDED THAT IT COULD BE A PRODUCT USED BY THEM???
Debonairs... I want a FULL refund. When I go to a restaurant and eat all my veggies but leave my meat because it tastes like water buffalo... will I then be charged for the veggies???