This app can help you if you change SIM card usually.

Sometimes, you choose SIM card of minor operator that called MVNO.
And you have to set "APN", via downloading configuration profiles from Safari, receive E-Mail.

It's need Internet, almost case using free Wi-Fi network.
But, you can not all find free Wi-Fi while traveling.
This app can help to set new APN even you're devices can't access to Internet.

This app bookmarks APN information released from MVNO.
You don't need looking for every single MVNO information if you have this app.
And this app also can note APN information on yourself.

Have a good iPhone & iPad life!!