Den Broadbands - Poor Internet Service

I have been using DEN Boomband continuously for the past * years now.
But from last month I have been experiencing often disruption of the Internet Services as sometimes the Router hangs up and the internet breaks. The problem vanishes after restarting Router but is very annoying as it happens several times a day.

I placed a request to replace the Modem & Router with latest DOCIS *.* combined device which is much better as it is installed in our neighborhood and works much better.
But even after requesting the same to following persons several times over the last few days the issue is still not resolved.