Hi, I had faced this problem too. There may be either of the 3 reasons -
1. Loose connection in jacks.
2. Faulty telephone line.
3. Broadband related problem in your area.
First the basic step u should take - check that all the jacks - telephone, splitter, USB, LAN are correctly inserted and that there is no loose connection.
Secondly, u should check out the phone line if there is any disturbance or
noise. If there is any disturbance or noise, it should be the telephone line connection which needs a look by BSNL technical people. Just register a complaint with the fault
booking number of your telephone exchange. [this is what happened in my case].
The other cause maybe that there is some problem relating to broadband in your area or city. For that u can just register a complaint with the broadband helpline. U can see if others in your area r experiencing similar problems.
Hope this helps.
Regards.