First Management Corporation review: Illegal billing

In September I had a clogged drain in my bathroom. I hired a plumbing company to unclog the drain. A pipe was damaged during the snaking, and First management (my management company) sent their plumbing company in to fix the damage. On October 20th I was sent a bill by first management for the work. The bill totaled $1575 and was lumped onto my monthly maintenance bill. When I asked to see itemized billing I was told it was not possible. I then directly called the plumbing company who had done the work to get an itemized bill but was told I they had been asked by first management not to talk to me but would forward a bill to first management who could then forward it to me. I received the bill which stated nothing other that $1200 for labour and $250 for a pipe. The plumbing company also claimed they had arrived at 8:30am and worked until 2:30pm. As I was in the apartment when the work was done I know that plumbers did not arrive till 9:45am and left at 12:30pm. leaving 3 hours of illegal labour charges. When I pointed this out to first management they told me they did not care and I was still required to pay the full bill they had sent me. When I mentioned that it was illegal to bill for hours not worked management told me that they would reach out to the plumbing company to get more information about the bill. At this point I was told that the 3 extra hours was for travel time. The plumbing company is in Woodside NY and I live on the UES. Which means they are charging me $600 for an 8 mile drive (round trip). When I pointed this out First management I was told that they could no longer have any direct contact with me. I have heard nothing since and I desperately want to get this sorted out. Many thanks in advance for your help.