If the neighbor modified the house without authorization, I asked the property management company to respond, but he didn't handle it well. Can I refuse to pay the property fee?

These are two independent issues. No, there is no problem without paying the property fee.

According to the relevant laws and regulations of our country, it is forbidden to put forward a design scheme, change the main body and load-bearing structure of the building, and other behaviors that affect the building structure and use safety without the original design unit or a design unit with corresponding qualification grade in the process of residential interior decoration.

You have reported to the property in your residential area that the property management department should immediately stop violating the relevant regulations. But if you are not satisfied with its handling, you can continue to ask for property handling. If you are not satisfied, you can go to the district real estate bureau and law enforcement bureau to reflect and seek a coordinated solution.

If your neighbor's decoration behavior causes you corresponding property losses, you have the right to ask him to bear corresponding civil liability according to law.