Unauthorised transaction from account

UberEats took R981.6 from my account on the 14th April when I didn’t order anything from them nor authorise the transaction. When I contacted them regarding this they confirmed that the order was placed from a different account but they said they cannot refund my money because the accounts are apparently linked. I have no idea how accounts could have been linked without my knowledge and nothing shows on my side. I didn’t get any explanation regarding this when I enquired. They gave me the first name of the person that did the transaction and said I should contact them myself but refused to give me contact details because of “privacy policies”. They could not explain how my account is linked to this person and how they were able to access my account details on the app. Furthermore, they did not provide any receipt of this orders when I requested for them but kept sending me repeated automated messages.