Failure to complete work and to respond to client

We paid the deposit to the supplier on 26 August 2015. They have started with the carport but failed to complete the work. We have a carport now of which the basic structure is finished, but without any chromadek sheeting, as they did not complete it. We paid half of the contracted price. There is also some rust damage to our swimming pool due to their welding. We tried so many times to contact Jakaranda staaldakke, but they do not respond to any emails and do not answer our telephone calls. It is almost 11 weeks since we paid the 50% deposit. We can not find their physical address to go there and discuss the matter. They have not contacted us or tried do explain or resolve the matter. We can not get hold of them at all! We do not understand their behavior! We have used them a few years back and can't understand what is going on this time! We do not know what to do anymore and are really disappointed and very unsatisfied. Please help!