Signal boosters not delivered - still waiting for my refund

On 1 May 2020 I ordered a cell phone signal booster 4G LTE – 150 sq. m. for R3,990.00 and a Wifi Booster for R606.20 (total cost R4,596.20) from Mobile Signal Boosters South Africa [Order #***] (May 1, 2020). After following up a few times to find out when I could expect delivery of my signal boosters, I was advised by the couriers that my signal boosters were being held by Customs as Mobile Signal Boosters had under declared the customs value and a penalty was payable. After a considerable amount of correspondence with Mia Davis, the Sales & Marketing agent for Mobile Signal Boosters South Africa, she advised on 17 June 2020 that I would receive a full refund for the amount that I paid for the signal boosters (i.e. R4 596.20), as there was no guarantee that my signal boosters would be released by Customs after the penalty was paid. I have followed up on my refund but, as usual Mia Davis has not responded – she has been generally non-responsive throughout the entire process. It is a month since I was advised that I would receive a refund but I am still waiting. I am extremely disappointed with the service that I have received to date from Mobile Signal Boosters South Africa and strongly advise against purchasing anything from this company. Furthermore, please note that they do not publish negative reviews on their website.