Please cancel my subscription and refund the amount

i signed up for the trial and cancelled the trial before the trial period ended. And i have used the trial for less then a week. But i was charged with 149.99$. I write so many emails to them asking for a refund as i cancelled the trial. But they are very rude in the replies they send me. I have been charged for a year through my amazon student account without any notification and they are not even ready to refund my amount. Please help.