Shocking Customer Service!!!

Received my online order & plugged in the hair straightener which gave a buzzing sound which indicates a fault. (Sent through a video of the buzzing sound) The item was collected & reviewed. I was told that that there is nothing wrong & this is completely normal which is incorrect. I have asked for a report from the manufacturer if this is in fact normal as I know someone who owns the same straightener & is silent when switched on as should be but was told that this is their most common item & they guarantee that this is normal. (Also confirmed with another reseller that there should be no buzzing sound) I was willing to have this replaced but was told a refund was already been done without my consent of agreement to the refund. I was charged the courier fee for the item to go back to them to be assessed as well which I should not be liable for as clearly there was a fault & they wanted to get rid of me as a customer hence the refund being done which I now have to wait 3-5 working days for. I have read many reviews with regards to faulty products & bad customer service. This was my first time purchasing from this company & I do not recommend purchasing from this company nor would I ever again! Customer service should be the key element to your clients that would recommend your company!