I bought more iCloud storage and it still says my storage is full

If the storage on your phone has reached its limit, buying more iCloud storage will not help. The physical storage on your phone cannot be increased in any fashion. It is fixed storage.

Did you read this article from which you asked your question?

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

You need to delete content on the phone if you are running out of storage.

I’m New to this company can you tell me how it works