My mobile phone is Apple 4. Why should I install Unicom 3G card? Sometimes I can only call and send text messages, but I can't get online? Seek the guidance of the great god, online, etc. Seek details

Determine why the iPhone can't access the Internet: 1. Ensure that the flight mode is closed; 2. Check the contents displayed in the upper left corner of the iPhone display. How many squares are there in the signal? Five squares are full. If there is nothing wrong with the signal, check what is displayed behind the operator. In the 3G network environment, E is 2.75G, and the letter O stands for the 2G network environment. Please try to move to another location or outdoors. 3. Inquire whether the Internet access status of the SIM card on the server is normal, and check whether the SIM card supports and has opened the Internet access service of the network access point; 4. Restore network settings; 5. Relocate the SIM card; 6. Restore the iPhone and make sure you are using the latest version of iTunes. Next, connect the iPhone. In the left column under Devices, click iPhone, and then click Restore in the Summary tab. Excluding the above methods, I suggest you change the machine for testing. If the SIM card cannot access the Internet on other mobile phones, it is judged that it is a card problem. You can contact the local manual customer service or go to the business hall to check whether the online data of the card is normal.