finally found the solution on s7 edge running android nougat, tried and testing, its working.
1.follow the instructions here to install and use adb
how to install and use adb, the android debug bridge utility
2.once it is installed and you have verified that it works (verification step is also given in the above page), just type the below command in the command (cmd.exe) window on the pc (phone should be connected by usb)
adb shell settings put global heads_up_notifications_enabled 0
basically its connecting your phone to the pc and sending a command through the pc emulator window to your phone system and disabling the heads up notifications.
If working for you all, lets spread the word to other forums too.
Tnx
rgds
mayur