Vishal Mega Mart — poor product quality

Address:

Ludhiana, Punjab

I purchased two driftwood trousers for rs800 on 8 april 2018.
They were looking good on me.
But i knew less about their quality.
I had to wash one of thenm 15 april 2018.
Soaked it in water for an hour with other clothes.
After washing what i saw was unbelievable... The colour of the new trouser had poured off totally...90 % of the trouser is now washed away.
The original colour was green and now it is light yellow in colour.
It seems that someone had painted the trouser and that paint has poured off with water.

Worst thing is that it had damaged my other trouser too which was in navy blue colour

Now what should i do??
I have two pics with this complaint.
First trouser which is almost yellow in colour is the one which i purchased on 8 aprik and the other one i purchased few months back