This article explains how to cancel your Amazon Prime membership through the Amazon website in a web browser.
How to Cancel Your Amazon Prime Membership
You can cancel your Amazon Prime account through the Amazon website. If you are not already signed in, you will be prompted to do so when you make a selection under Your Account. Enter your details and select Sign In. Once that is done, you can begin the cancellation process.
Hover your cursor over Account & Lists and select Prime Membership.
At the top of your screen you will see a menu bar with the member's name, enrolled plan, renewal date, and general membership options. Select Manage My Membership.