False advertising

Today i received an e-mail from Dotsure: "Get 50% off your first three months' premiums.Don’t give Murphy the satisfaction – protect your parts by signging up online and get 50% off your first three months' premiums.*" I signed up via their online platform, but once I received my policy documents and debicheck authorisation sms I noticed that it's for the full premium. I sent an enquiry and was phoned by one of their consultants whom claims that the e-mail I reacted on does not exist, I will not be getting 50% off my first three premiums!!! Is this false advertising or what? I feel *******