They informed them that they had to remove a tool called Callkit, that allows to implement VoIP calls into their app.
Any app that uses Callkit is refused by apple for the Chinese market.
The message stated: “Recently, the Chinese Ministry of Industry and Information Technology (MIIT) requested that CallKit functionality be deactivated in all apps available on the China App Store.”
Despite this announcement, VoIP is still allowed in China, but the ease of use of Callkit seems to be the issue. Some Human Rights activists suggest that even though China doesn’t want to officially ban VoIP, they want to make it more difficult to use.
It is not the first time Apple had to comply with Chinese demands as they removed last year Microsoft’s Skype among other VoIP apps.