Falsely claiming refund for the work done and cancellation of agreement for poor work done

Respected sir/madam. construction company and client entered into agreement of residential building construction as per the clients Plan in April. technical and commerial details was agreed by both party and signed on particular date and work was started with the minimum advance as per client request,after the stage completion we have raised the request for payment by posting the completion of work and seeking clearance for the next stage .client happily accepted the stage clearance and mentioned that loan will get sanction in 3-5 days and payments and advances will be cleared and thanked for the work done. Now after the starting of the next stage client started querring for every step to stop the work this is not correct that is not correct it is not as per the practice , he is claiming that my uncle is claiming that columns are wrong But not even a single time they(client) made us to visit /meet the complainant about work done. now client is stopping the work and asking us to vacate all the structure and give them back their site plain and they want their money back. we have taken all the necessary steps which civil industry seeks and also have appointed a B.E civil engineer to moniter and a skilled supervisor to supervise the work. Now we are really shocked to listen from client that instead of appreciation we are getting messages from client and demanding for refund and settlement. Please help us suggest us how tomove forward. regads.