Builders Warehouse does not respect its own return and refund policy on defective products

I bought a Lalela inverter last year September. By December the unit started performing below expectations. Sent it in for repairs and it was returned in late January. The unit worked as expected. Again, by March, it started working below expectations. I was now not interested in another repair and requested for a refund (either in my account or in store voucher). They refused. I approached the CGSO, but they have been ignoring them as well - it’s been over 2 months with no response. At this point, it’s clear they do not entertain complaints of defective products you buy from them. They even have a policy about returns and refunds but they do not live by it.