Instruct: Classify the given review as either positive or negative.
Query: Not working well

We bought this collar for our dog and the two of the same brand's cat collars and they are not working. We put the collars on after giving each of them flea baths and we are still discovering fleas on them. The collars do not seem to be killing off any new ones that find their way onto our animals. I'm getting a little frustrated because we've tried a number of different methods without a whole lot of luck.