I cancelled and deleted an account when it turned out I was already billed. How can I get a refund for the account I no longer have?

I was on free trial for the PRO account, which did not work out for me. I cancelled my subscription and deleted my account on the day before it expires (so I thought). However, It turned out that I have done so after I was already billed. I did not receive any notification that I will be billed, so I missed cancelling before the actual transaction took place. Now I do not have an account, but I do have a charged credit card for it. How can I get a refund of my money in that case? I am not very eager to pay for an account I no longer have or want.

The account I had before was: hn32002@yahoo.com . Appreciate your help.

Kind Regards,
Hristo Nikodimov