Note that there may be more steps needed than just cancelling the subscription and deleting the app. See: https://support.robokiller.com/hc/en-us/articles/360027065591-How-can-I-disable-RoboKiller-on-my-iPhone-or-Android-device-
Also, regarding the absence of the Cancel option, see the following from How to cancel a subscription from Apple - Apple Support
If you don’t see Cancel, the subscription is already canceled and won't renew.
and
If you cancel a paid subscription, you can keep using the subscription until the next billing date.
Also, a subscription that is already cancelled will typically have wording in fine print similar to "Expires on [date]" rather than "Renews on [date].”