• How to recover fees for my intellectual property already used ?

Hello Sir,
 I am an Architect practicing independently from home.
 Last year I had difficult clients. I had agreed to do the design & Drawings and 
stage wise visits and quoted my fees accordingly.
 Two of them have cheated me by using all my drawings but when asked for remuneration earlier they postponed & now denying giving excuses ,when all work is over. I request you to help me out to recover my remuneration for the work already done.