blockbuster.com blockbuster online promised free 30 day trial, I cancelled, early, they charged my credit card anyway , Internet

After viewing a Blockbuster ad online on 7-12-2012 advertising FREE 30 Day Online Rental Trial I decided to sign up

My plan was called the total access plan  which allowed 3 rentals at a time by mail or in the store for $19.99 if I liked the service after 30 days.

I decided after 2 weeks that i did not like the service and returned all movies and cancelled.
Blockbuster.com  acknowledges the official date of cancellation as 8-7-2012 which was 25 days into
the trial.

Blockbuster.com charged my credit card on 7-12-2012 $21.44 when they weren't supposed to until 8-13-2012, 30 days after that when the trial period ended.

Blockbuster.com refuses to refund the $21.44 saying once they charge your card, they can no longer give a refund. They then went on to try to sell me other services while they were stealing from me.
They also gave a lame excuse that they no longer offer the free 30 day trial.

The fact is that on 7-12-2012 they were offering that and need to abide by it.