I used to be a sales person at Broadmeadows in the Computer department in 2006. Being a salesperson is very very tough. Their wages are very low and they have to work very hard to get the small commission. You have to understand that Sony Playstation has very low commission. In fact most of the time stores actually loose money selling them. They only make money with add ons like games, warranty, etc. Although this is no excuse for poor customer service, there is no motivation for the salesperson to give you the royal treatment.
While I was working at Broadmeadows, even if a product actually lost me commission, I will still provide excellent service to my customers. So you have every right to complain. Harvey Norman have been fantastic in providing low income earners an opportunity to buy things on no interest payments. They have been doing so for many years. They also sponsor events, sports and charities. I still highly recommend that you continue to shop at Broadmeadows. If you were not satisfied with the service then send a letter to the Manager of the store or even go higher and send a letter to Sydney where the Harvey Norman headquarters are.
By the way, the reason why I left Harvey Norman was to pursue a career in the banking industry and not for any other reasons.
Good luck and I hope you have better experiances.