Thanks FurryNutz for your response.
>> What Hardware version is your modem? Look at the sticker under modem.
Modem Name : DSL-2730U
>> Link>What Firmware version is currently loaded? Found on the modems web page under status.
Firmware Version : IN_1.02
>>What region are you located?
I am from Bangalore, India
I had complained to my ISP before without luck. However, I will ask them to check your points again.
I will check other options you have mentioned and get back to you.
I have one more question: From the symptom I have mentioned above, does it look like a modem restarting issue?