In the matter of the "friendly neighbourhood MTNL hood" :lol; and line issues, it pays, after the linesman are done sweating it out in the open and come to check in on you, to ask them in for a glass of water and tea to show your appreciation. My father's been using MTNL telephones for the last 60 years and our issues got a priority during the worst of times. But this 10 minute off and on thing (have you timed it exactly) leads me to suspect your modem, or server problems at MTNL's end. Oh boy, if it's the latter you are done for, change your ISP at the first opportunity. Kidding, but then maybe i am not.