They do not want to refund my money

So basically I purchased a laptop from Computer mania Cavendish Square branch. On the 9th of February 2016. Firstly the machine was advertised with having a high end quality processor but I received an inferior model of what was advertised. I then contacted the sales manager of the branch to tell him my concern and issue that I was having and that I was unsatisfied with the machine that I have purchased. I then told him I want to have the machine brought back for a cash refund as I paid hard cash for it. I was then told that I will not be getting my cash back but a eft will be **** directly into my account. It has been 3days after I have returned the machine and there has been no communication from there side to me whatsoever. I contacted them a few minutes ago in regards to my issue and I was treated with rude and unprofessional service from the branch manager Desmond that was mentioned previously above. I have still not gotten any response in regards to where my money is or anything in that regard.I am extremely upset and disappointed in the level of customer service and service quality of this company from sales all the way up to head office management levels. Please help me.