https://arstechnica.com/gadgets/2018/05/apple-cracks-down-on-callkit-enabled-apps-in-chinas-app-store/

A new group of apps in China's App Store is facing scrutiny from Apple. According to a report from 9to5Mac, the iPhone maker is curtailing apps with CallKit framework due to a "newly enforced regulation" from the Chinese Ministry of Industry and Information Technology. Apple started sending notices to developers whose apps use the CallKit framework, notifying them that CallKit functionality isn't allowed in China due to the new regulations. Developers reportedly have two options: remove CallKit framework from their apps, or remove their apps from China's App Store entirely.