Data light off and Link line is on though the real problem is with the line

I'm using Airtel broadband and Beetel modem 110BX1. Since last week, the Link light on the modem would suddenly go on and off, and the network gets disconnected, and then a minutes later, the Link light will go on but the Data light will go off. Since the Link light is on, I was misled that the problem is on my side, and got the modem replaced, but again I'm facing the same problem. If I launch the Windows Network diagnosis, it also says "Network cable is unplugged" even though it is not. I have tried with a new network cable as well. But the real problem is not with the computer, I know this because it works fine when I take the laptop to office. Why should the lights glow wrongly, that too on two different modems, and confuse me, the customer care, and even the Windows network diagnosis ?
Any help is much appreciated.

In advanced options Management
disable TR_069 client box.

If no improvement :
ADVANCED OPTIONS:IN DSL
uncheck box ADSL2+
Keep Bitswap enabled.
SAVE reboot.
feedback.

Unfortunately when the internet is not working, the modem url 192.168.1.1 also doesn't come up.
When I pinged 192.168.1.1 it says
Reply from 192.168.1.2: Destination host unreachable

When the internet came up I was able to open the modem page and disabled TR_069 like you said. I'm waiting to see if the connection will die again or not.

Connection again had been dead for 2 full days even with TR_69 disabled. I had not been able to open 198.162.1.1 during this time. Today somehow the connection has come back. It is clear it is problem with the line only, isn't it?

When internet is working Backup the settings of the modem
to say C:/My Documents/110BXI working.

mention the ISP.