No Help

I bought a car amplifier and subwoofwer which is combined together on Friday the 20th of May. We installed it yesterday on the 26th of May only to find out that it's not working correctly. It goes on, you can see it's getting power, but the amp doesn't put the sound through to the sub. So basically it's just on and not doing anything. I took it back and they explained to me it doesn't have a warranty because it was a self install. My problem is that the sub/amp was never tested when I bought it and I told them how would I know that it wasn't working before I bought it. And they just said sorry they can't help me how do they know that it's because of me that it's not working. I came to the store within the 7 day out of box failure. I was only able to install it yesterday, because I didn't have someone to help me. I feel that this is unacceptable seeing that the product was never tested before I left the shop. I didn't know that it was supposed to be tested. On the 21st of May I also went and bought a car radio they tested it, when we installed everything I saw on the invoice that it was also supposed to be tested. Now I'm sitting with something that's not working and can't do anything with it. This happened at Cash Crusaders Potchefstroom at River Walk centre