Incorrect installation of windows

Quoted for the supply and installation of aluminum windows, the supply was good, but the installation was not.

When the first rain came, the windows leaked terribly, causing damage to our floors etc. When we called him, he simply answered that we must do the waterproofing and said he told us this, but he didn't. So we asked him, "Why did you install the windows knowing that no waterproofing was done!" Then, he wanted to charge us to remove the windows so that another window installation company could come and correct it! After numerous messages to Ernest who was un-helpful while rain was causing further damages we eventually had to pay another Aluminium window company to remove and install them properly which they did perfectly.