How can I cancel the charge of .99/mo that I’m paying for iCloud storage

Like this:

Downgrade your iCloud storage - Apple Support

Good luck!

Welcome to the Apple Community. 

You can change the amount of storage by selecting a new plan right from your iPhone, iPad, iPod, Mac, or PC (for example, a 5 GB plan to replace a 200 GB plan). The downgrade will take effect after your current monthly or annual subscription ends.

iOS

1. Go to Settings ➔ Apple ID(Top) ➔ iCloud ➔ Storage ➔ Manage Storage.  
2. Tap Change Storage Plan.
3. Tap Downgrade Options and enter your Apple ID password.
4. Choose a different plan to use when your current storage plan expires.
5. Tap Done.