Disgusted with Discovery Card

On 17 Feb I contacted Discovery Card about an amount of R503.25 interest that was billed to my credit card on 13 Feb, to inquire why and how this interest was calculated, as it is incorrect in my opinion. As the person at the call centre was unable to assist me in a meaningful way, I asked to escalate the matter to a specialist, who in turn assured me that Discovery Card would contact me via email within an hour to explain the interest calculation. I am still waiting and have had no response two days later.

My previous credit card statement dated 14 Jan 2020 had a total amount owing of R20424.79 and the minimum payment due date was 8 Feb 2020, by when I had to make a minimum payment of R1022. I made two payments (both of which are reflected on that same statement) of R15000 on 15 Jan 2020, and a further R4000 on 30 Jan. I thus paid R19000 after the statement date and well in advance of the payment due date, leaving only R1424.79 of the total amount owing not paid by the payment due date. I fail to see how this amount could generate interest of R503.25. I also fail to see how it can be permissible to calculate interest on the total amount owing if that is what happened, when most of it was in fact paid off before the payment due date.