Legal Question in Business Law in California

No. When the restaurant gives you a menu it implicitly is telling you that the listed prices are the ones you will be charged. The "subject to change" language you quote means that they don't have to tell you before increasing prices in the future. It does not mean they can conceal increases that they have already made and that they intend to charge you.

At common law a price quote or list price is an offer to deal. That common law rule is altered by various statutes designed to protect consumers in California. For example, Business & Professions Code section 12024.2 provides:

(a) It is unlawful for any person, at the time of sale of a commodity, to do any of the following:

(1) Charge an amount greater than the price, or to compute an amount greater than a true extension of a price per unit, that is then advertised, posted, marked, displayed, or quoted for that commodity.

(2) Charge an amount greater than the lowest price posted on the commodity itself or on a shelf tag that corresponds to the commodity, notwithstanding any limitation of the time period for which the posted price is in effect.

Sounds like 'false advertising' and fraud under the Business and Professions code. You could file a lawsuit, using the menu and your bill as proof.

You could file a complaint with the Department of Consumer Affairs, the Attorney General, the police and DA, etc.