Will never enter a Gadget time ever!!!!!

So I decided to visit a gadget time store for the first time as I just wanted to see what it is that they were stocking as I was looking for a gift to purchase. I came across a modulator that I could use in my car as my factory fitted cd player can only play cd's.I asked the sales assistant at the time to tell me more about it as I was rather keen in buying it.I asked the person ringing up the modulator and his name is Mahomed if that I am unhappy with the product may I get a full refund and his said yes I can.i tried the modulator and it did not serve the purpose what I was looking for as the quality is not great. I then went back to gadget time the next day and asked for a refund. Firstly the cashier on duty does not know whether he can do the refund and then calls the manager from his cell phone and does not even apologise.The manager then rock up 15minutes later, no apology for keeping me waiting on him. I then explain to the manager that I purchased the modulator using a DEBIT card and that I want a cash refund and he then tells me that he cant he needs the card that was used to purchase as it the company policy. If I was told that then I would have used cash,he walks away!!!!