You have to watch some of those people. About 10 years ago I had a new liner inserted. Even assisted in pulling the liner down inside the basement while two guys fed it down. I had to leave before the job was done. About a year later, furnace tech was cleaning furnace and said your liner is missing. Those thieves removed it and nobody knew. The furnace company arraigned install. But claimed they didn’t know who they were. Liars. But due to time lapse, nothing could be done. Make sure you stay till they leave.