My storage payment completed but I don’t see the storage in my settings. It’s still saying I’m out of storage

Are you confusing iCloud storage with device storage?

What's the difference between device storage and iCloud storage? - Apple Support

Device storage is located on chips within your iPhone. It goes everywhere that your iPhone goes. It is fixed for the life of the phone, and there is no way to increase it. Many types of things require device storage – iOS, apps, music, photos, videos, etc.

iCloud storage is located on Apple's servers. It's for making iPhone/iPad backups, and for storing copies of things (like photos, videos, and files) that you want to automatically synchronize between multiple devices.

If your phone has 128 GB of device storage, and you paid for a 2 TB iCloud+ plan, you would still only have 128 GB of device storage. If you are using iCloud Photos, and you have so many photos and videos that you are nearly out of free device storage on your iPhone, you may want to select "Optimize iPhone Storage" in Settings.

Manage your photo storage - Apple Support

"When Optimize Storage is turned on, full-resolution photos and videos are stored in iCloud, and, when needed, space-saving copies are stored on your device."

When you pay for more iCloud storage, that gives you more space to back up and sync data. It has no effect ton the local storage on your iPhone.

What's the difference between device storage and iCloud storage? - Apple Support

It is not possible to add more local storage to your phone.