Ultratech Super - Cement quality is very Bad poor

I am building my house with ultratech super cement.
The cement was thick in the ground floor but I got my first floor shingled on **rd December.
When I opened the center on **th January, all the ice is cracked and very weak and is falling apart even after hitting it with a stick.
I complained to the engineer from where I had taken the cement. He also visited and checked the strength but we felt that the engineer met the shopkeeper and told him that it is okay to do it like this.
Please tell me how this is possible.
I have lost a lot of weight
I called the main and other cement shop people and they said that it is the duty of cement.

Please suggest that I file a case against the company.