storage

Please read the following support document -> What's the difference between device storage and iCloud storage? - Apple Support

If the issue is with internal storage, you will need delete data off his phone to gain back memory.

IF the issue is with icloud - then you can purchase more icloud storage to backup and sync to the cloud.

Links to refer to:

How to check the storage on your iPhone, iPad, and iPod touch - Apple Support

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

Manage your photo and video storage - Apple Support

You rented extra iCloud storage and that does not increase the capacity on the iPhone.

I sometimes really wonder why people keep asking this over and over again since there’s a difference between iCloud storage and the storage on your iPhone, I guess they don’t really know the difference. I sometimes feel sorry for them because they buy iCloud storage and then realize that they cannot use it and wasted money.