Best option is that dont let lineman know you use the landline for internet.
I had a lot of problem with MTNL connection, both landline and broadband. I had taken my complaints right up to the GM. Every time, the problems were directed to the lineman. Fortunately, the problems are resolved now. Though, I don't get 2 Mbps as per the plan (I get 1.6-1.7 Mbps), I don't mind. This is better than the lineman fiddling with the connection and messing it up completely.