BAD SERVICE/REFUNDS

Purchased products last week Wednesday ( 18 November 2015) from Mr O's in Merrydale Avenue. The one part was not needed and my husband returned it to the store on the same day. He then asked the sales assistant to swop the goods for other parts needed for the vehicle. The sales assistant then swiped my bank card again instead of doing the exchange. A return was apparently done and i would have to wait 2 - 3 days for the money to reflect back into my account. When I called the branch on Friday afternoon (20 November 2015) the gentleman assured me that my refund was made and that I should wait a bit longer. I had been checking my account the entire weekend to ensure that my money was returned...and to my surprise NOTHING had been returned. I have called the store a few times and every time i get different excuses. Even that my money was infact refunded already. I have called everyone that I have needed to call and yet they still do not admit to the fault been with them. WHY DO I HAVE TO RUN AFTER THEM FOR MY OWN MONEY???? I would also like to know why a transaction that was made on a Wednesday only goes off on a Saturday!!!???? This is Utter ********!