Bad service

My dad passed on in Feb 2025,my mother and I went to vaal mall branch and we where advised to get the letter of authority to close the credit card, it was the first week of March.we managed to get it and went to Vanderbijlpark branch,they didn't ask for it but processed the claim and it was approved but later in April my mom got an sms to pay the balance.we went back to the branch to ask why do we have to pay when my dad had an insurance on the credit card.the reason we got is that they tried to debit in March and they didn't get the funds.How do you debit a deceased bank account when we already went to the branch to report?my mom is not working ,she is a sassa pensioner, how is she supposed to pay for something she reported in time?