Paving destroyed

After installation of fibre under my paving, frogfoot simply loosely placed the bricks back into place. After a previous hellopeter complaint, they came back and added a very white, brittle cement that is quickly turning to dust. The cement has cracked and crumbled and the bricks have sunk into the ground due to a lack or soil compacting. I think it needs to be professionally repaired at their expense. If they did a proper job from the start it would not have come to this.