Hey! I was in the exact same boat a couple of weeks ago. My folks’ insurance provider only accepted faxed documents too.
I didn’t have a fax machine either, so I looked online and found this super helpful article: https://beebom.com/best-fax-apps-for-iphone/. I picked one of the apps from the list, scanned the forms using my iPhone, and faxed them right from the app. It worked perfectly, and everything was sent in minutes. You should definitely give it a try!