Hello santosh
Sorry to hear this is happening
I am guessing you have tried an alternative handset in the socket
Also checked for any loose connections
If so and its still not working, Then I will need to get an engineer booked in for you
If you don't mind, I will need to send you a private message to pass security
If you can check the purple envelope top right of your screen that would be great
Regards
Gareth_L