Still issues after canceling.

I cancelled our medical aid on 1 November 2021. On 3rd November the installment went off like normal. I phoned moment health and made sure if it would be the last payment (the one that already went off on the 3rd of November) to which the lady confirmed. Now, on the 2nd of December 2021 another installment went off. We are not even covered anymore but you want to take more money. When I phoned, they said that we are paying in arrears. Since when does a person use a seevice and only pay later? I would like the money to be refunded, as it was not supposed to be deducted.