Credit Check not refunding a debit for a cancelled service

I am experiencing a very unpleasant treatment from this company. I cancelled their services on the 16 May 2024. They confirmed that it is cancelled and the debit order of R1840 will not go on the 20 May 2024. On the 20th they deducted from my FNB account. I got in touch with them on the 20th and a confirmation was made that they debited after the cancellation was made and promised to refund. I have been waiting for the refund to date. I'm very unhappy with the whole thing and I fear that they will continue deducting my money.