Overpriced, overcomplicated and doesn't take responsibility

I needed a shower mechanism in my bath. The original quote was costly, and the solution was overcomplicated. The work was good, but the contractor is difficult to convince. Long story short, he had put in a mixer which caused issues in the pipes of the house, so a non-return valve had to be installed by an external plumber. The plumber was initially blamed for causing the issue and that left us with no warm water for 5 days. I then decided to cancel because I wasn't confident in the work of the contractor with the idea that I can at least get the money back for the mixer. But the contractor refused to give the money for the mixer back and refused to take responsibility for the issues caused. So now I have a mixer without a receipt (so I don't confidence that the mixer even works). I would have given 1 star but at least he put in the original taps for me. I just don't like his attitude, it's so difficult to get him out, nobody wants to struggle like this.