Non adherence to credit agreement

On 13 Dec 2020, i used my Capitec credit card but it kept on declining. I then called Capitec. I was told that i have made a payment arrangement for the loan, therefore it affected my credit card. Capitec sent me the message on 7 Dec 2020 that they could not debit for loan account. I then called them and asked them what was the agreement between me and them when taking the loan as i told them that i am getting paid on the 15th so why they wanted to debit on the 7th? i then requested them to set the debit order for the 15th as it was. Therefore by so doing i made a payment arrangement and I cant use the credit card, whilst are the ones who did not adhere to the agreement in the first place. What informed them to debit on the 7th because is not me?