This is no legal issue so I hope I can help ;-)
First, the way you described about how the rental company charges less for new comers is very common. They are betting a tenant would be less likely to take the hassle to move after living a year there. It's pure business. You, of course, have the right to move according your contract terms.
Second, you should read your lease agreement. On that, it should describe how you can terminate your lease. Don't assume the ways others terminate their leases would apply to you. For example, the agreement may say that you need a written notice. Then you need to put it in writing, instead of just sending an email. In another word, everything you are asking here, you can find the answer in your lease agreement.