I hired a fence guy to put a the fence around our commercial building since it is required by the county. The contractor hire a sub-contractor welder to put build the gate frame. The contractor did not pay his sub-contractor. The wood fence that we originally bid and pay deposit on was too heavy and have failed county inspection 2x so the fence contractor switch to chain link gate with privacy mesh. He did not tell me that this is now an extra charge. I just found out from the final bill. He removed the wood gate, replace it with chain link with privacy mesh, and that pass the inspection. I don't want to pay the fence contractor the balance for 2 reason. First, He did not pay his sub-contractor who is now threatening me that he will file a lien on my property. Second, he is charging me extra $550 for the chain link and privacy mesh. I agreed to the wood gate which is more expensive than chain link. Since he could not get the wood gate to work and he switched on chain link. I assume that contract the price remains and just switch material. Apparently, he said that is extra cost and he is now threatening to file a lien on property as well. He kept telling me to ignore his sub-contractor. What is the right thing to do?