Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This phone doesn't work!!

I bought this niden 2-line wireless phone system with 4 phones, and only three work at a time, the 4th won't register no matter what I do. After a few months, I'm having trouble on all handsets with the volume suddenly dropping by 50% so that I can't hear who's on the other line and have to switch handsets mid conversation.I am now shopping for another manufacturer as this phone is too unreliable for my business.