Account settled, but can't refund credit.

So, I settled my account on 30 June 2020 and now have a R50 credit. I also received the "paid-up" letter confirming that the account has been settled and that the account is now closed. Upon asking, via the Whatsapp number they provided, for a refund of the R50, I am informed that they can't refund me. How convenient is that? They give you a settlement amount bigger than what it actually is and then don't refund you the credit. How much money are they making? After querying this on 2 July, they said they will forward my query, to who knows where and advise on the feedback. Up till now, no feedback. And I still don't have my credit refunded.

Even though the account is settled and supposedly closed, I can still access the account on their website.

I am also sure that I will receive the standard "We will call you back" response.