Q:

Unfamiliar prompt when inserting new prepaid SIM card into iPhone in China

While visiting Shenzhen, China yesterday as a tourist I acquired a prepaid +86 SIM card from China Unicom. Everything seemed to work out fine, but I am wondering about one observation:
When the sales clerk inserted the new SIM card for the first time the iPhone brought up a full-screen prompt with (if memory serves) a two-line text in Chinese on dark background and apparent "OK" and "Cancel" buttons. He pressed "OK" before I could take the phone back and that was it. This was at an official China Unicom store and the transaction seemed professional and legitimate.
What could that prompt have been? I don't remember this exact behavior from my iPhone on previous occasions of inserting various SIM cards, but then how could a specific SIM card insert a proprietary user interface? I would normally have taken a screen shot at this point for further inquiry, but the process went to fast.
So my question is this: what might the prompt have been and is there reason to be concerned from a security perspective?

A:

I just have the sim card of China Unicom.
The text is "尊敬的客户，欢迎您使用中国联通业务！"
Which means "Dear customers, welcome to use China Unicom business!"
I don't think there will be any security issues.
It is a sim application that can handle business（e.g. order data plan) with cellular data off.
Go Setting-Moblie Data-SIM Application you can find more.
I don’t know more technical aspects.You can see the wikiSIM Application Toolkit

