Stylerush hair straightener

Hello, I'm really so disappointed with this salon as they have no business etiquette or any kind of proper morals to give us as consumers a new straightener if the one I bought isn't working any longer. The straightener I bought was a "Stylerush" I paid R1500.00 cash for it last year on November 4th 2016 with a 1 year warranty. This salon took my straightener in on the 11th of October 2017 to fix it because I mentioned my straightener went off for like 10 seconds. It sounded as if it was sparkling inside the straightener and this stylerush wasn't as hot as it setted when I first bought it, it seemed warm as I set my hair. When I received the straightener on 18 October 2017... the straightener had glue which is still on the straightener and I said to myself okay they fixed it.I then washed my hair and setted my hair the plates was so loose and it felt like it was just not setting my hair or maybe like a cheap straightener where you have to straighten a set of hair over 5 times.... I then called them and told them they made it worst so they said I must send it back in, I got really upset and told them to replace the straightener as it's on warranty and they aren't fixing it as it should be fixed. They refuse to replace it but keep telling me it's working. The manager whose name is Vincent told me they didn't tamper with my straightener at first they just put it on to see if it's working and don't open the unit. I said if they didn't open it why is it springing and why is there glue stuck on to it they kept telling me they didn't tamper with it. I then sent an email because they weren't calling me they kept telling me I must contact the manager Vincent, but he gives me these long stories & I am telling him the unit is not like how it was before it not setting my hair like it used too set it.. he says I must bring it and they want to set it, I went to the salon he wasn't in and I couldn't wait, so they told me to take it and use it and if it not working I must call them, they don't seem to contact me via telephone but only by emails... I then said the straightener is still the same. & I will send a video of me setting my hair, their response was I must come back to the salon to speak to Vincent and let them set my hair.... they don't want to believe me and keep making excuses of exchanging such an expensive straightener as I can't afford another one and don't want to go and get more problems with it after the warranty is finished. I'm so tired of talking to them & I don't know what else to say to them cause everything I say, they turn it around and make me seem like a liar. The unit is expensive..... it took me along time to save that money and go and buy the straightener so I really don't expect this kind of treatment from such a upmarket salon!!!!