bait-and-switch 
noun [mass noun]
The action (generally illegal) of advertising goods which are an apparent bargain, with the intention of substituting inferior or more expensive goods: [as modifier]: a bait-and-switch scheme...
- It may involve such tactics as billing for more hours than were worked and bait-and-switch staffing which means providing excellent staffers at first and then replacing them with less qualified personnel.
- Wallach and other leaders of worldwide popular dissent have been making the same argument about bait-and-switch diplomacy for a decade.
- This ploy was yet another example of the public being duped by a classic governmental bait-and-switch scheme.