Audible — I want my money back

I don't remember I ever signed up for them. I never delete emails with information about registration on websites, so I checked it to find proofs I never signed up. But I did. For free. I never was notified about being charged or something like this. If I didn't check my bank account, I would never find out about these charges. So they take my money each month. And it's not cheap. Now I'm trying to reach their customer service but they don't answer.
I hope they will fully refund.