What to do in a case where a business does not want to refund nor exchange a bad item that they have sold to you

I bought hair from a hair vendor, 3 months later I complained because I did not like the quality, I waited for that long because I was taking it to a hair specialist to treat the hair because I thought maybe I’m doing the wrong treatment. But that hair specialist even confirmed that the hair indeed is of bad quality, mind you the hair advertised is not the same quality sold. When I shared the matter with her she said I should bring it in so we can find a way forward, however due to me not being around from the time I complained till 2 months back because of work, I found time to take it to her. There’s been no response for over a month and when my manager reached out that’s only when they started 2 minutes communications with me, there’s been back and forth and no resolution, even though I had asked that may we sort out the matter in an amicable manner. Today they telling me that they don’t see any problem with the hair, therefore no refund nor exchange