Customer pretty belligerent. Has not responded to demand payment in registered letter. He seems to be a serial abuser of contractors. Never wanted to call former contractors to "fix" problems. Always tried to get our company to fix things "in addition to" originally requested scope of work. It got to be a series of verbal change orders that he resisted paying. When we complained about deteriorating communications, offered to wrap up current work and terminate the relationship, the customer immediately got vindictive.