I purchased extra storage however my phone is saying that it still has no space

icloud storage is cloud storage.

every apple user will get 5GB free storage.

let's assume

you have purchased iPhone xr 64GB. (SO 64GB IS IPHONE STORAGE.NOT CLOUD STORAGE)

when your device storage is full.(IT MEANS YOU HAVE USED 64GB/64GB)

NOTE: PURCHASING ICLOUD STORAGE DOES NOT INCREASES YOUR IPHONE INTERNAL STORAGE

ICLOUD STORAGE IS CLOUD STORAGE TO KEEP YOUR OFFLINE DOCUMENTS IN CLOUD..

icloud stores.photos and whatsapp backup and contacts many more..

iCloud storage is for offline keeping of documents. It has no relation to the internal storage of your phone, except you can move some things from the phone to the iCloud and free some space. Stuff to put in the iCloud: pictures via iCloud Photos, movies, documents, iCloud mail.

To free space on the phone go to Settings / General / Storage and review how much room each app occupies. Unused apps can be offloaded, which erases the program but keeps the data, or deleted altogether: as long as the app continues to be available in the App Store, can reinstall later. Some apps, especially social media, do tend to store lots of stuff in their caches; you need to go in their settings pages and do what it takes to purge those caches.