If you are getting notifications from VantageReservation, then your Mac is infected with adware. VantageReservation is adware for Mac.
VantageReservation changes setting in your Mac. First, VantageReservation installs a browser extension in your browser. Then, after VantageReservation hijacks your browser, it modifies settings in the browser. For example, it changes the default home page, modifies search results, and displays unwanted pop-ups in your browser.