After clicking on Shop Menu, a new tab will open in your browser. Here you will see your payment info scroll down to the bottom of the page and select Nintendo Switch Online.
Now you will be on a page that gives all your membership details like the expiration date, the deadline to turn off automatic renewal, and the amount due. To continue the process, select Turn Off Automatic Renewal.
Finally, you will have one more box that pops up, asking you to confirm your selection. To continue the process, select the red Turn Off option on the right-hand side.