Worst service ever

My mom bought me a UV light machine for gel nails for Christmas and was told that if it did not work of if I did not like that one, that she could get a refund for it. We brought it back as it did not work nor did I like the piece of ******* (no offense mom), only to be shouted at that the lady did not say it and that we could not get our money back. After a long fight with the lady pointing her honey finger at a small piece of paper saying no refunds behind the till where no one can see, the lady calls the owner to come check if we are right. Now we have to wait longer for the lady to check that we are telling the truth, that the machine does not work. What happens next? The owner tells us how to use it, although we know how to use it duh, only for her to realise it is a piece of ******* that she sells. Never in my life will I get told to Shut up again by a little shop lady. Never shopping there ever again.