Control box

I bought a vw t5 control box from manic auto and I was promised an exchange if it's not working as long as it's within 7 days and 2 days later when I call them and inform them that their box is not working they told me they can't change it because it's electrical part,when I tell them what I was told when I bought the box,they say the sales person is new and she made a mistake.The lady I spoke to on the phone was very rude.