1st two month free with 24 month contract

I have been contacting ADT about the 1st 2months free seeing that I re-entered into a 24 month contract with them. no one gets back to me. I see my account was debited end of March I signed a 24 month contract end of Feb and alarm was only reactivated Mid March yet the full amount was deducted end of March and not pro Rata as the agent told me. I did not get the two months free as advertised. I have sent e-mails, called their call centre and they tell me only my agent can help me and they will ask her to call me. I have not received any response. I sent a complaint on their website and still no response. why did I not get 2months free and why am I charged for a full month when was alarm not activated in the beginning of the month?