Have you tried the following sir
Press and hold the volume down and Power buttons at the same time until you feel a vibration (about 10–15 seconds).
When you feel the vibration, release the buttons, and then immediately press and hold the volume down button until you see a large exclamation mark.
Once the exclamation mark appears, press the following four buttons in this order: volume up , volume down, Power, volume down. Your phone should now reset and restart itself. (It might take a while for the reset to finish.)