Shocking service with no project management

The owner of this company promised that the construction of our pool would be complete after four weeks. Four weeks have now passed and we're still sitting with an incomplete shell after we've paid him 80% of the quoted price. He is never on site and his workers start working after 11am most days and finish at 4.30pm on the days that they do arrive for work. They've been absent more than they've been on site. The owner refuses to communicate promptly. He never answers his phone when you call him and only responds to whatsapp messages when he feels like it. He is definitely a very, very poor project manager who is a jack of all trades and master of none. I would not recommend his services to my enemies.