D-Link — Modem complaint. Under waranmty

Had purchased the above modem on4.6.2020 through M/s. Flipkart.
Now the modem is showing complaint. Often the net connectivity goes and the red light comes and goes. Not steady. I had three times complaint to BSNL and they checked all the lines and told that no complaint on their side and it is due to the modem complaint that the internet comes and goes.
So please arrange to replace it at the earliest. It is under warranty. T