Contractor job was not good should I pay?

[Bailey Coleman]

I bought a SFR in a decent neighborhood on the east side. I am an out of state investor so I had to manage the project renovations while not being there. The contractor I hired did not do a good job and I feel like they are screwing me over with half *** work. I already paid 50% of the agreed price and I still owe him like $800. Is it okay not to pay them because the work was not good to the point where I do not think the house is going to appraise for what I want it to. They also took too much time doing the renovation and threw away all the reuse-able material that I bought away in the trash. This experience with this contractor has been a nightmare. They also left trash in the house. I had to have a friend take everything out. Has anyone ran into a problem were the contractor did not perform. I am thinking about not paying them due to these reasons.