Who is stopping my connection

Hello Everybody,
I am karan from Delhi, India. I am facing a problem since last 4 months. my OS is Win 7 (Ultimate). I am using an internet connection from "Hathway". I exactly do not know what type of connection it is. The persons of Hathway just laid a cable and attached it to my pc. I need to enter username and pw to a tiny software they have installed in my pc to use the internet.

The problem.
After using internet on my pc for some hours, the connection become unavailable. When I ping, it shows connection timed out "or" destination host unreachable. Secondly, If I use my connection for 2-3 hrs and then shut down the pc for lunch or dinner and came back after around 20-30 minutes, then there is no connection at all and same message when I ping.

I have used the following but no improvement :-
Start, Run, CMD to open a command prompt:
Reset TCP/IP stack to installation defaults. netsh int ip reset reset.log
Reset WINSOCK entries to installation defaults: netsh winsock reset catalog
Reboot the machine.

I do not know what to do. The technicians from Hathway have came and checked my pc and cable many times but with no good results. On their request, I have formatted my hard disk 6 times but nothing improved.
I have also changed my lan card but in vain.

Other pcs of my neighbours from same line are working fine at same time. Can anybody help me?
Also I am not good in English so sorry for that. I am improving.