When you're using expo you cannot bundle your own native extensions. At my previous job we used pjsip. This extension uses JNI and native calls in iOS via objective-c. You can't bundle native extensions when using expo. You're locked to their prebuilt ones.

To use your own extensions you have to eject/or start a new application with their own native libraries. For most of what expo does you can use the unimodules libraries, they're quite good in my experience.