Storage

You cannot increase or in any way modify the storage capacity on an iPhone. Whatever it had when bought is what it will have forever.

If the capacity is filled up, you will need to delete content or transfer it off the iPhone. See here: link-. How to check the storage on your iPhone, iPad, and iPod touch - Apple Support

If you want to use non Apple storage services, you will need to contact whoever service you want to use and ask them.