deleting phone backups in storage

Yes. There are instructions in: Manage your iCloud storage - Apple Support

Yes, you can do this directly from your iPhone or iPad.

1. Go to Settings and tap on your Apple ID name/picture at the top
2. Tap on iCloud
3. Tap on Manage Storage
4. From the list find Backups and tap on that
5. Tap on the device name of the backup you want to delete (wait a few seconds for it to load)
6. At the bottom you will see the option: Delete Backup