Manoj's distance to the server is less than yours, the physical line condition too may be better, hence, his line stays stable even at those high sync rates. (V)DSL is very much distance dependant.
Discuss with airtel on lowering the sync rates or trying a different profile for your line and see if that helps.
The issue here is due to factors that are out of your control. There isn't anything you can or haven't already done or tried at your end. Only airtel can properly diagnose the root cause and fix it, provided they can/are willing to do it.