Netflix stopped allowing subscriptions through Apple some time ago, and only people that have never cancelled it are still charged by Apple for it, so its likely you are subscribed directly with them, and you would need to go to their own website to manage it.
"How to Cancel Netflix"
https://help.netflix.com/en/node/407
Similarly for other subscriptions that may not be charged through your Apple account.
What do you see for the charge in your payment method's statement for this other app? It should provide an idea at least of what the App is.
Charges for subscriptions charged through your Apple account will appear as "apple.com/bill" on your payment method's statement. Anything else on your statement that does not show up as "apple.com/bill" is not billed by Apple, and by extension would not appear on your account.
Also note, if you are the Family Organizer in a Family sharing group, subscriptions started by other members may be charged to you, but not appear in your subscriptions. If you are a Family Organizer, look in the accounts of other family members for the subscriptions.