Unethical practice. Review on Livspace

We engaged them for furnishing our three-bedroom apartment. There were days of discussion before they understood what we wanted and zeroed in on the price. We agreed to the price. A contract was signed. They committed to finish the work in a certain period of time. After some time, they began work. They had mentioned a certain date for completion of work. They finished about 90% of work some three months after the due date. The quality of the work done is satisfactory. For the rest of the work, we had to pursue them vigorously. After a great deal of stressful effort, they did some of the work and did not do the rest. They agreed to refund the money for work not done. Then comes the surprise. They sprang up a document wanting to us to sign that we shall not “make any negative, defamatory, disparaging, or adverse statements, remarks, or comments about each other or their representatives, either directly or through another person, on any public forums or media platforms. Any existing statements of this nature are agreed to be removed”. I suppose this is why one sees good reviews only. We decided to not sign any such document so that we can actually review them. So, they are withholding the money. Note that this is refund for not doing agreed work. This is unethical.