Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Unreliable Product

I used to work next to a rack of servers. I got these headphones, and for the first week they worked very nicely. Then the right earphone started to do weird things. I got a refund and tried again.The next pair worked fine for longer time (months). But now when you turn the noise cancelling function on, they make significantly more noise than before, to the point that if you are in a not very noise place you have to turn it off. Still helps in flights, but that's not aceptable for a $100 headphones.