I Need Amazon to Cancel an Unwanted Prime Membership and Refund £14.99

I recently discovered that I have been signed up for an Amazon Prime membership, even though I never intended to subscribe to this service. Yesterday I noticed that £14.99 had been taken from my account for Prime, and this was completely unexpected and without my clear consent. Since noticing the charge, I have tried to contact Amazon customer service, but I have not been able to get through to anyone or resolve the issue. At the moment, I am still being shown as a Prime member even though I do not want this membership. I request that my Amazon Prime membership be cancelled immediately and that the full amount of £14.99 taken from my account be refunded. I would like written confirmation once the membership has been cancelled and the refund has been processed.