MTNL
Link light is blinking

I am using mtnl broadband service. My link lights is the problem it is not stable, it becomes stable for 20 or 3 minutes bt after it goes then it blink then comes, it is happening with me form a month. i called 1504 so many times bt nothing happen they give me complain no. and says that there lineman comes but no one came i even called AREA MANAGER bt nothing happen can anybody help me