Dissatisfied service

I bought Russell Hobbs iron at Hifi corporation menyln branch which is still new until the 1st day when I decided to use it, in the middle of my ironing it just stopped working at its own. I went back to the shop for exchange and they told me that they will liased with its manufacturer and revert back to me in 2 weeks which they did. And they told me The iron had a faulty fuss which it was attended. I decided to contact Russell hopps regard as I did not understand what the shop were saying to me. And the lady at Russell Hobbs told me the problem could be that the appliance might not be check for quality tests before sending it to the retailers. My concern is if the iron is still new and it already gave me that frustration, what would be my guarantee that it won't happen again. I mean this new product is already been tempered with hence they opened it while fixing the problem. I expected this product to be exchanged not fixed. I even asked the shop to write me commitment that if I experience the same problem, they will be liable but they refused. That really raise a huge red flag to me as it proved that they don't want to account for this error at all. I'm talking about quality products for that matter, as I have lot of Russell Hobbs in my house and I trusted them but after this struggle I can't say same thing. All I need is exchange or give me surety of what they performed in the iron. I can't be stuck with the faulty iron which was never of the quality tests as they will be telling me is out of guarantee /warranty period...