Product: Debt collection

Dear Sir/Mme : In the middle of XXXX, a solar installer company called XXXX XXXX called me to solicit my business to stall solar panels on my roof. The purposes of this, we all know, was that we could go green to protect our environment. Personally, for me, they promised that I could reduce my electrical bill by a very large percentage. Plus, there would be some tax benefit from the government. Before that, XXXX XXXX had partnered with XXXX XXXX XXXX XXXX  and they came together to start everything with me, and later to finance the project. They offered many good terms, such as, no up-front payment, low interest rate for the loan, no payment until the project was done and the system started producing electricity to replace the power from my power company, and there would be a 20-year warranty after the installation to cover the maintenance, repair of the solar system if anything would go wrong in the future. They also promised to repair my roof if any damage was done during the installation process, among other favorable terms. Those were common terms that could have been offered by any other solar installers then and today, because the government was, and still is, backing this kind of projects for the good of the society and the environment. So, I took their offer and signed agreements with both XXXX XXXX and XXXX XXXX XXXXXXXX XXXX to let them work on the project ( please refer to XXXX bill to me as evidence # 1 ). 
In XX/XX/XXXX, XXXX XXXX sent a group of technicians to my home address to do the first partial installation, then they left. I waited for a long time for them to come again to finish the work, but they never came again. Even worse, soon after that, I lost contact with them. After a while ( about in the beginning of XXXX ) I learned that the installer company had declared bankruptcy and no longer in business. I reported this to XXXX XXXX XXXX promised to find someone else to finish the job. Eventually, they found a XXXX-based business called XXXX, to finish the solar project. XXXX ( please refer to XXXX email correspondences to me as evidence # 2 ) contacted me on the phone once and sent me a confirmation email each following month to confirm with me they were actively looking for someone in their network and in my area to do the job. But recently suddenly, XXXX decided not to shoulder their responsibility and refer my case to a collection company ( please see the collection letter as evidence # 3 ) for debt collection. This is not fair to me, and very wrong of XXXX XXXX to do this. 
I would like to make it clear here : {$27000.00} is the total cost for the whole project, including the material cost ( the solar panels ), the installation fee, the hood-up procedure to the power companys power grid, and the warranty service for the next 20 years after the installation. Since this is an unfinished and abandoned project, I would definitely not pay {$27000.00} for the collection. 
I started with a sweet dream of having solar power installed on my roof top ( that is what it was meant to be then, and still is today ), now it becomes a nightmare : I do not have a completed, working solar power system, instead, I am deep in debt to the bank. There supposed to be no immediate big cost to me. Now my electrical bill is the same, in addition to the huge debt I am in. My rights as a consumer have been seriously violated