The newly bought American version of the unlocked iphone4S has a signal when plugged into Unicom's 3G card, but there is no 3G logo. You can make phone calls, but you can't send text messages.

The American version, Japanese version and other foreign versions of the iPhone are divided into locking and unlocking, which is also called network lock. If there is no lock, you can insert the card directly for use. If you have a lock, you need to paste it (the card paste needs to correspond to the system version, for example, the original 4.0 version of the card paste cannot be used after upgrading to 5.0). The principle of the card paste is actually to disguise the signals of domestic operators as those of foreign operators and be recognized by mobile phones. Therefore, if you want to use the Internet function, you must turn on cellular data, 3G function and data roaming at the same time. I suggest you try to modify the settings and see if they can be used. (In addition, it should be reminded that there is a built-in card sticker on the market, which sells the locked machine as an unlocked machine. If conditions permit, I suggest you check it and simply judge whether you need to open the above items before surfing the Internet. There is no need to unlock the version. ).

These foreign operators will have network locks in custom machine, and there are two ways to use them in China: unlocking and pasting. Unlocking is divided into official unlocking and software unlocking. There is no difference between the official solution and the normal authorized use of mobile phones, while the soft solution is to crack the permissions of mobile phones by software, which can not be guaranteed to be completely cracked at present, that is, there may be some defects in use. Card stickers are for unlocking mobile phones. By sticking a card on the number card, the signals of domestic operators are disguised as those of foreign operators and recognized by mobile phones, so as to achieve the purpose of use. However, this method has compatibility requirements for mobile phone systems, card stickers and operator number types. For example, the card sticker of ios4.0 cannot be used after the system is upgraded to 5.0, and a new version of the card sticker needs to be developed. The initial card can only support 2G function.

So please also make sure what your mobile phone is like, whether it is unlocked or not, and what it is unlocked. Soft solution needs to set parameters, please follow the requirements of soft solution program. If it is officially unlocked or factory unlocked, just like using licensed products, if you can't use SMS, see if the number of SMS center is set correctly.