Sign in to the Amazon account with the Prime membership you want to cancel. In the upper right-hand corner, go to Sign in. A drop-down menu will open. Click the yellow box that says Sign in.
On the Prime Membership screen, look for an option titled End Membership under the Manage Membership menu. Clicking this will not immediately terminate your membership, but it will take you to a new screen where you can begin the process.
Amazon will guide you through a series of confirmations before you can cancel your membership. In a last-ditch attempt to stop you from leaving, Amazon will ask you again if you're sure you want to cancel. There will be a button labeled with today’s date.
Choose End on [Today's Date].
Amazon Prime Day 2021 runs from October 13-14 this year.