Solution to iPhone 4G network interruption

It frequently appears that there is a 4G network but cannot access the Internet. Even when the network is being used, the network is suddenly disconnected. The 4G network displays normally but cannot be used. Sometimes the network is suddenly disconnected and restored suddenly. Occasionally it can be solved by switching airplane mode on and off.

In addition to the problems with the 4G network, occasionally the mobile phone cannot receive any signal at all at the same time. There are also frequent situations where the signal is full and suddenly there is no service and the search is in progress, and the mobile phone signal is always No, there are usually only two bars of cell phone signal at home.

These two problems are very distressing, especially when you need to pay by mobile phone or make an urgent call. It is embarrassing when the network and signal are suddenly cut off when everything is normal.

I have tried inserting the SIM card into other mobile phones and it can be used normally. I have eliminated SIM card problems and phone bill arrears. I have also tried re-inserting the SIM card and restoring network settings, but the same situation as above still occurs. , hoping to get an answer.