Never using Uber again

I requested an uber ride on the 31st of December, chose to pay by card as I had no cash on me R170and I immediately canceled the ride upon realizing how long it would take for the ride to arrive. Uber claimed to have voided the transaction when I canceled the ride, however they still deducted the full amount from my account, and have not refunded me my money back. Upon contacting them they keep telling me that I shouldn't charged for that and yet they are refusing to refund me.