Can't get through to ***** Department and Uber still keeps *****ing my money!

On 7 September I received an email to say my Discovery Credit card had just been debited with R1800 by Uber. I had not used Uber. I immediately reported this on my phone app and called the ***** Department to report this. They told me this was a common occurrence because the Uber site was not secure. They confirmed that my card had been cancelled and no more transactions could go through on the card. I have just received my credit card statement and discovered a further R1600 was debited from my card on 20 September. I have been trying to get through to the ***** department since last Friday to inform them of this ********** transaction and to find out what is going on but cannot get through and no matter how long I hold on and the recorded message is "We are experiencing very high call volumes" this is very worrying! What shocking lack of service - and who knows how much more Uber will debit my card in the meantime! Will they keep on going until my credit limit has been reached? The worst thing is , Discovery are aware of the general problem with Uber but they are still allowing the funds to be drawn from my card, even though it has been cancelled!