My storage says full but I have over 30G of memory availability. How do I fix this

Which storage are you referring to?

How are you confirming the 'available' memory.

You may be mixing iCloud storage with storage capacity on the phone itself. By default you get 5GB of iCloud storage which you can use for backups, data transfer, file sharing, etc. If you're trying to backup a 128GB iPhone to your 5GB iCloud storage account it may be that's where the problem lies (you can purchase additional storage space on iCloud if you need it).

They probably are. I have at least 80GB free on my 6S Plus. I have 200GB on iCloud to use.