Money disappeared and they refuse to refund

After many days of trying and asking them for a straight answer as to where did my money go , what lead my account to go on a negative balance leading to money disappearing from my account because capitec is a non-overdraft account meaning no negative balance is allowed, despite the transaction that they claim has resulted to it had declined due to insufficient funds they went ahead without my consent and allowed it to go through. they today told me they are not going to refund me claiming it was a tap to pay even after I had provided them with proof of the declined payment and fees charged. Im not letting this slide i am escalating this to banking ombudsman. For a good 5 day of back and forth nothing was resolved