Mass Stores / RCS Group - extremely poor customer services and false advertising

I purchased an item at Dion Wired Gateway on 17 Dec 2018 based on a Mass Stores promotion - 10% back on your invoice. This offer was valid until 24 Dec 2018 and the understanding was that the credit will be passed on my January statement. I received my January statement on 13/01/19 and there was no credit reflecting. Upon failure to contact Dion Wired Gateway telephonically, I then took this up with Game Gateway as I had used a Game card to do the purchase. Olivia of Game asked me to send my written query via email to RCS Group merchant services which I did on 17/01/2019. I received an automated reply advising of a 48hr turn-around time for a response. I eventually went in the Dion Wired store on 02/01/2019 only to be told by Sharon (sales manager) that the matter will be resolved & that I need to take this up with their customer service advisor Nelly. After having made several attempts to contact Nelly, I received a call back to advise that there was a lack of communication between Mass Stores and RCS Group hence the issue I was dealing with. To date this matter has not been resolved. All customer service agents that I have dealt with make a call or 2, send an email or 2 then that is where it ends. You leave messages, send emails and they just don't bother to respond. I have now taken the onus upon myself to directly with with a team leader at RCS Group, who also have been dragging their legs with this matter. Customer service no longer seems to exist. I suggest any customer that made a purchase with Mass Stores under the Black Dot Promo follow up and ensure that the required credits are passed because believe me, nobody cares. It seems Mass Stores just does false advertising just to secure a sale!!