False advertising free activation mant

I signed up for a LTE contract, and they advertised that I would get the activation month for free, but I waited about 1.5 weeks for the package to arrive, and when I finally started using it, it was 27 April, and I got exactly 3 days for free, and not a month as advertised. Now they billing me for May, after I cancelled my service with immediate effect when I found out their free month was only 3 days. This is the way they cheat and rob their new customers, and falsely advertise benefits that you can never fully utilise.