This guide at Seeking Tech will show you three ways to get to the cancellation screen from your PlayStation 5 if you want to end your subscription to PlayStation Plus Essential, Extra, Deluxe or Premium.
1. The first method is to go through the PlayStation Store App.
Once you open it from the home menu, go to More > Subscriptions PlayStation Plus.
2. You can also go to the same cancellation page from the PlayStation Plus App.
After opening this app, head over to More > Manage Subscriptions.
3. For the third and final method, open the Settings menu of your PlayStation 5.
Afterwards, select Users and Account > Account > Payments and Subscriptions > Subscriptions > PlayStation Plus.
Once you are in the cancellation page, select the Cancel Subscription option over the next two screens, and then Confirm Cancellation.
The final page will ask if you want to provide feedback as to why you are cancelling. You can provide a reason if you want to. Otherwise, select the Continue option.