How can I cancel Audible?

I just found out that I have been paying for Audible for months and I don’t remember signing up for it. I do have traumatic brain injury but as you can tell, I’ve never used the service and I’ve been charged, and I would like to have those charges reversed and the subscription stopped. I tried to stop it through Amazon, but they said that it was purchased with you. Please help me.

[Re-Titled by Moderator]