This sounds like a LA based call center that looks for people that need home improvement work.  They, in turn, contact a real contractor based on the exact type of work to be done.  It's a sleazy way to do business and the calling is obviously illegal.  But you can get some work done at a very attractive price IF you carefully screen the contractors.  I had an asphalt driveway replaced by pavers about five years ago and the work was fine at about 60% of what local contractors were bidding.  But I knew someone with a major construction company who helped me keep on top of the job.  However I've also had an outfit show up to bid on a reroofing project and they didn't even bother bring a ladder to inspect the roof (they didn't get the job).  The biggest complaint is that the calling company remains anonymous in all this and there's no way to get them to stop calling.  Highly likely that the number is spoofed.