Nobroker Interiors - Pathetic Customer support delay in work and charged for wrong items installed

I have given my interior project for my first house to nobroker interior service.
According to contract the project should be completed on (took * months)**th july **** but still now *st August the major part of the work is pending.
They have installed shutters of different colors than what we agreed on during design phase and documented in the contract.
Designed dressing unit wrongly.
As per the contract, delay penalty should be paid but now refusing to pay.