The 14 day cooling off period During the first 14 days after you have entered the contract you have the right to leave the contract without incurring a penalty.
All that is required in California is to notify the listing agent in writing.
The easiest way out is to sit down with the real estate brokerage the realtor works for and discuss breaking the agreement. Many reputable brokerages who wish to keep a favorable relationship with your business will agree to peaceful contract termination.
Simply send them a letter or email stating that you are no longer working with them effective immediately. You are not obligated to work with any realtor you don't like. Cut contact after sending the message and contact the new realtor.
If you're set on canceling, send a formal request in writing, either via email or certified letter. Be sure to include your property address, the date, and a clear statement that you're terminating the agreement. If you want to work with a different agent in the future, be clear about the termination timeframe.
Terminate the listing agreement. This part is easy. Just send a letter to the broker stating that you wish to take the home off the market and that the brokerage/listing agreement signed by you on x date is hereby terminated. Do not include any other language or information.