I just bought a new iphone12. I was paying .99 for the monthly storage. It wont let me go in and cancel my subscription.

Downgrade or cancel your iCloud storage plan - Apple Support

Settings>Tap your name>icloud>manage storage>change storage plan

Sometimes it takes a moment to load change storage plan.

If you can't select Done

If you can't click Done, make sure you are signed in with the same Apple ID as your iCloud storage plan. You can also try following these steps on a different device.

Did you set up this iPhone with the same Apple ID as you had on the previous phone?