Ordered at Edgars online and did not get complete order and neither my refund.

I placed an online order nr *** on 6 th of May 2020. I did not get all the goods I paid for because Edgars was out of stock and I would get a refund as per the invoice received with the part order. Today is 28 August 2020 and I still did not get my refund for the goods not received. Customer care keeps on referring me to a refund I received for a previous order. I don’t know what to do anymore to get my refund.