The travel agent will probably claim the price was an invitation to treat not an offer, which may be considered contractual. No offence has been committed unless the agent knowingly tried to mislead you, decide what you want an explanation and (guarded) apology or compensation. If compensation can you show the agent set out to knowingly mislead you, eddie makes a good point, and you may find it very difficult to receive any compensation, if it is an apology try writing again and ask for an explanation by a specific date and send by recorded delivery and as ladybirder & boxtops say perhaps contact their trade organisation if you get no satisfaction from the agent.