No supply and no refund

On the 26th July, I placed on order on Leroy Merlin's online shop. The total of the order and delivery charges were charged to my credit card. I then received an email informing me that, due to a stock error on their system, they could not supply the complete order. The email stated that a refund was on its way to me and that I would receive 10% off my next order. The promised discount did not materialize. The refund was not processed On the 23 August. I sent an email requesting details of the refund. It took a further four emails before I received a response. On the 29th of August. I received an email that basically repeated the details of the email I received on the 26th July. To date, I have not received my refund.