How do I cancel Amazon Prime?

Try this:
Just sign on to Amazon and select "prime" then select "Manage prime" you should be able cancel there.
Hope this helps.

To end your Amazon Prime membership:

1. Manage Prime Membership .
2. Do one of the following:
   • To cancel a paid Amazon Prime membership, click End membership. Note: Paid members who haven't placed an Amazon Prime eligible order are eligible for a full refund. You can't receive a refund if any of the household members have placed an Amazon Prime eligible order.
     
   • To cancel an Amazon Prime free trial, click Do not continue. Note: If you don't cancel your Amazon Prime free trial, you will be automatically upgraded to a paid membership plan at the end of the trial period. You can find this date listed on the left-hand side of the Manage Your Prime Membership page. You will still have access to your Prime benefits until this date.