Modular Kitchen Drawings altered without my consent

Hi I gave a contract to install a modular kitchen at my house to a delhi based company. The price quoted by them was 3,75,000+ 14% taxes. They asked my to pay 1,75,000 in cash and balance through cheque with taxes. I did so but they deposited one cheque in the personal account of proprietor's brother without my consent. Also, They altered the drawings without my consent and interchanged the shelves and boxes. Also they took the wrong measurements of the kitchen and installed kitchen unprofessionally. Now they are hiding from their duties. They are not ready to come at a conclusion. I have paid all the amount to them and they are not ready to provide me with the bill. I wanted to ask whether I should file an FIR first or send a legal notice. I am asking them to take back their kitchen and refund the amount but they are not ready to do so. Also will cash payment made by me is a valid proof Now I want to ask whether I can sue them for this. They were not ready to accept the mistake. After 3 months of pain they finally accepted the mistake.