Refusing to replace a defective laptop - my job is entirely online and is now at risk

Coming onto Facebook about this because endless calls, messages and going into store is not helping me get my matter resolved:

I purchased a laptop 15 days ago for work from HI FI Corp Baywest, and was sold a defective laptop and HIFI Corp Baywest is refusing to replace my laptop and what's worse is that they tried to rip me off and ***** from me by offering to replace my laptop with a laptop worth less than the amount I transacted into their account when I purchased my laptop!

My job is entirely online and this refusal to replace it is putting my job at risk.

HIFI Corp please play fair and replace the broken product you sold to me so that I can work!

If anyone has direct contact details of anyone in top management please forward them to me as nobody at HiFi Corp is working to get this matter resolved in a timely manner.