If that is what the contract says and no specific clause that post death fees will be charged then charges should include up to and only including the date of death so you are due a refund I would say.
What annoys me so much is that WE are supposed to honour our side of the deal but care homes dont have to.
We were promised that my Mum would go on outings and trips, that there would be plenty of activities, that they would sit out in the garden on nice days, that she would be treated as an individual and her needs would be met. We were told that her whole care package would be centred around her and we would be invited to regular meetings to discuss her care. None of this happened but we paid our bills by standing order every month. We were just fobbed off every time we asked anything.