Good morning, I took out car insurance with Discovery and realised I was happy with my current insurer

Good morning, I took out car insurance with Discovery and realised I was happy with my current insurer. I cancelled the Discovery insurance within 24 hours; they called to confirm the cancellation, and I thought we were done. Twelve days after my payday, I noticed an unauthorised debit order—it was Discovery and debited along with an insurance transaction(Insure Act) I knew nothing about. I called them for a refund, but I haven't received it. Every time I call, they say the refund will take 24 to 48 hours, but nothing has been received.