Cal. Pub. Util. Code § 491
Unless the commission otherwise orders, no change shall be made by any public utility in any rate or classification, or in any rule or contract relating to or affecting any rate, classification, or service, or in any privilege or facility, except after 30 days' notice to the commission and to the public. Notice shall be given by filing with the commission and keeping open for public inspection new schedules stating plainly the changes to be made in the schedule or schedules then in force, and the time when the changes will go into effect. The commission, for good cause shown, may allow changes without requiring the 30 days' notice, by an order specifying the changes that may be made on less than 30 days' notice, the time when they shall take effect, and the manner in which they shall be filed and published. When any change is proposed in any rate or classification, or in any form of contract or agreement or in any rule or contract relating to or affecting any rate, classification, or service, or in any privilege or facility, attention shall be directed to such change on the schedule filed with the commission, by some character to be designated by the commission, immediately preceding or following the item.
Ca. Pub. Util. Code § 491