Sometimes, Apple hide APN setting from iOS devices.
Why? In my opinion, Apple preferential treatment relationship to Major Mobile Operators, not Users!
Almost cases, iPhone & iPad is so smart. Like case of choose major mobile operator, users have no problems.
Case of choose minor mobile operator(like MVNO), users have to set APN manually, because Apple don't show APN setting for us.
This specification is bad, especially change SIM while traveling.
Because installation of config profile need Internet, almost case using free Wi-Fi network.
But, we can not all find free Wi-Fi while traveling.
I thought this is good opportunity for me to create good convenient app and sale on App Store.
But this app rejected from Apple.
So, I'll release source code to Open Source.
You can use this app if you have a Apple Developer Program License.