Requesting a refund for cancelled subscription or change plan to monthly from yearly & refund

I installed the adobe Reader and subscribed for 7 day free trail and then 99$ for yearly 

but I was going to cancel it before my trail end and I thought I gonna receive an email before the free trail subscription ends but in reality it doesn't happen and I got charged for 99$ for an yearly term even though I was not willing to get an yearly subscription.

I kindly request you to cancel my subscription for the current year and proceed a refund or if that is not possible please convert it to monthly plan 7.99$ so that atleast I get refund of 91$ because I seriously don't want a yearly plan which I am not going to use even for one day from my 365 days I have paid for.

please help me in this matter.

It's a lot huge amount of money for nothing services taken in return.

I can't let it go in vain.