Instruct: Classify Amazon reviews into positive or negative sentiment
Query: This does not work with cordless phones

I ordered this to use with my cordless phone and headset and discovered when I received it that it only works with corded phones. It plugs into the telephone receiver, then the telephone cord plugs into the other side of the Rf filter. I tried it on my corded phone and it didn't help reduce the buzzing sound in my new wireless headset. I then called Plantonics and they're replacing the headset, so I can't comment on how well the device works when you have a functional headset.