Legal Question in Business Law in California

Signing an order with a plumber amounts to entering into a contract. However, the damages for breach of the contract would be small to none if you cancel promptly and the plumber is able to find other work. I would recommend contacting the plumber and politely asking to cancel and see if you can get his agreement to do so without charge, or perhaps with a very small charge. You aren't in a real strong bargaining position, but if the plumber has other work and wants to protect his reputation, he might be quite cooperative.