Confused billing subscription choice.

Today, I log in my account and choose start 14-days free trial. Then, system told me I've already enjoyed it. I think it will be fine to purchase a month subscirption. However, the website directly choose the yearl billing without clearly statement. And I click "continue"  button. Now, I was charged for about $260. I don't think it is fair. And I don't see any cancel option or refund option for me. Anyone could help me? 
Thanks.