Neighbour erecting 12 ft boundary wall

Sir,

  Already we have boundary near about 6ft height , now the neighbour is fighting we me to increase the boundary more 4 to 5ft, i tried to make them understand that if you increase the height of wall it block the light and wind,and already boundary is there then why it is necessary to increase the height.

                       My neighbour doesnot want to listen me and always ready for quarrel .

What can i do please guide me.