What if Xiaomi's mobile phone can't access the Internet?

I suggest you put this mobile phone card in another mobile phone to see if you can surf the Internet.

Call for arrears

If you can't get online, please ask the operator whether you owe money.

Turn on the data flow switch

If it can be used, please put it into Xiaomi mobile phone, turn on the data flow switch, reset the default in Settings-Access Point APN, then restart the mobile phone and try again.

Clear all data

If you still can't surf the Internet, I suggest you back up your data, restore and clear all the data (turn off the phone, press and hold the volume+power on button to resume), upgrade your mobile phone to the newly developed system with a line brush, and don't install the application that requires root permission for the time being to see if it can return to normal.