350-a. False advertising. 1. The term "false advertising" means advertising, including labeling, of a commodity, or of the kind, character, terms or conditions of any employment opportunity if such advertising is misleading in a material respect. In determining whether any advertising is misleading, there shall be taken into account (among other things) not only representations made by statement, word, design, device, sound or any combination thereof, but also the extent to which the advertising fails to reveal facts material in the light of such representations with respect to the commodity or employment to which the advertising relates under the conditions prescribed in said advertisement, or under such conditions as are customary or usual.
The show is advertised as starring Josh Groban. He is therefore part of the product they are selling. Unless his absence is pre-announced for specific dates prior to the availability of tickets for such dates, ticket buyers are entitled to a refund.