Nedbank double debit my account with NO authority!

I lodge a complaint via email to nedbank for a double debit they took from my bank account. I did not authorize nor agree to the double debit. Then a few days later I received a sms saying my account is in arrears! How is this even possible? You took twice and still sms me saying I'm in arrears.

Absolutely shocking that after after 15 days I still have explanation for the double debit after receiving a email saying that they looking in to it. And absolutely no response for the sms.