A listing agreement should include a termination clause to outline conditions under which the property owner or real estate agent can end the contract early.
"You may cancel this contract at any time before midnight on the day seven days after the day on which you sign the contract, or before a later day if specified in the contract that is after the later of the day on which you sign the contract or you receive the facility's disclosure statement.
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.
Any amendment should be explained in-full so that all parties are in agreement. Discuss the Amendment. The broker and owner should meet and discuss the changes to the listing agreement. Write the Amendment. Once a verbal agreement is made, the amendment should be written. Sign and Attach to Listing Agreement.
First off, without a defined expiration date, you didn't have a ratified listing agreement. Second, in California, as of 2024, you cannot have a listing agreement term for longer than 24 months, and if you essentially had an indefinite listing agreement, this would be unlawful.
Termination clauses can always be customized but standard ones are included in almost every agreement.