Exceedingly dishonest about payments. They will quote you and promise you one thing, and then not honor their commitment. They will get you on-site for a service call, and if it be4comes complicated, will verbally promise you an hourly rate, or an increased flat rate, and then when it comes time for payment, they will deny ever making any such commitments, even if your have names, times, and the end-user's signature.

If you try to secure your rights to payment you were promised, they will stop using you. They go through technicians like water through a sieve as a result of this.