if i bought icloud storage why does my phone still say no storage ?

Your phone itself is running out of space. The storage on the device has nothing to do with iCloud storage and buying more iCloud storage doesn’t help.

See this for more information.

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

It is because you cannot increase what you physically have on iPhone.

iCloud Storage is meant for backup and syncing.

Read here => What's the difference between device storage and iCloud storage? - Apple Support

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

iCloud storage is independent of iPhone storage. If you need more space on your phone, you will need to delete something.