Back up iCloud storage to my iphone

First off, I would not like to purchase iCloud storage, in no way is that option, and it will never be an option. I have a 1tb iPhone 13 pro. I’ve maxed out my 5 gb of icloud storage and need to back up to something. Cause now I get this warning saying iCloud couldn’t be backed up cause it’s full or something like that. I would like that something to be my 1tb iPhone, that is why I bought the phone, tons of storage, no reason to pay anybody anything when there’s a full terabyte just hanging out in my pocket. Any suggestions on how to do this are welcomed and appreciated. Anyone suggesting “it’s only $2.99 a month” can go elsewhere. Thank you, god bless America, and all the other countries as well. Amen.