Bad Customer service

I bought and had a Telefunken radio installed in my car. That was the great part and it was done professionally and quickly, but after a few weeks of getting to know the product, I realized that there was a usb wire missing. I went back to ask for it, they just rep**** that I should have done so earlier, that it's not their fault and that I must have lost it. But this is where I am a perfectionist, I kept everything even the boks. They just send me away without even trying to help.