Vodashop Noorwood refusing to cancel contract

My sister app**** for a contract phone @VodaShop Norwood on the 14 July 2021, due to the looting around the country my financial situation have change, I decided to cancel contract due to affordability, I'm within the 7 days to cancel my contract but the manager refused saying is not allowed and how is going to sell a second hand phone

If I can't afford anymore what should I do hang myself? She is reckless and do understand customer needs,