是iphone4。通常当你插进去其他公司的SIM，手机就会叫你输入 unlock code ，这个code 是ATT给的。

你没有unlock code，怎样unlock 你的手机？

下面是ATT客服里的有关部分：

Unlock your AT&T wireless phone or tablet

 

You may need to unlock your phone or tablet before it will work on another carrier's network. Devices bought from AT&T may be programmed with an IMEI (Subsidy) lock that prevents it from operating with other compatible wireless services.

To unlock your device, just complete our simple online unlock request form and we'll take it from there. Business customers can request an unlock code for a business device at att.com/biz.

AT&T will provide the necessary unlock code upon request for devices requiring a code, provided AT&T has the unlock code, or can reasonably obtain it from the manufacturer, and you have met the unlocking requirements provided below. AT&T may complete your unlock request within 48 hours, but may take as long as five business days.