No word from Woolworths about refund

I've sent two emails in as many days to the Woolworths customer support team requesting a refund owed to me for a difference in the amount debited from my account for an online order and the value of the goods that I actually received. I have had no response. I am utterly appalled at their shoddy service and unsure why they cannot accurately track the stock they have available at their DC to avoid overcharging customers for items that aren't delivered.