I would like to formally lodge a complaint regarding the poor service I have received from Showspace

I would like to formally lodge a complaint regarding the poor service I have received from Showspace.co.za I recently purchased a heater which, after being fully assembled, does not work. I have attempted to contact your customer service team daily, but to date, I have received no response apart from automated email replies stating a 24-hour SLA – which has not been honoured. The lack of communication and support has been extremely disappointing. Based on my experience, I would rate your service a 1 out of 5. I would appreciate urgent assistance in resolving this matter and receiving a functional product or a full refund.