I would check disconnection code as a first thing. Run "nRF Connect" application on Android device, connect to your target and then see the Log. Log can be accessed by swiping right the screen with Services of connected device or through "three dots" next to DISCONNECT button, then choose "Show Log". If if you are using Android tablet then turn it to portrait position and Log will appear automatically.
@NIDHIN: Please provide some more information about your phone, the hardware board you are testing with, which firmware, softdevice, which app, how did you test.
