The SMS center number 86 automatically changes to 82, resulting in the inability to send text messages.

Based on your description, it is recommended that you check the following steps to troubleshoot:

1. It is recommended that you click SMS-Menu Key-Settings-Advanced Settings-SMS Center Number to reset.

2. It is recommended that you try dialing a friend to see if you are in arrears.

3. It is recommended that you try to see if other cards can be used normally when inserted into your Xiaomi phone.

4. If the problem still cannot be solved, please back up your data, enter recovery to clear the cache, user data and all data. After entering the system, do not restore the data for the time being and send a text message directly to try.

5. If the problem still cannot be solved, it is recommended to back up the data and flash to the latest development version to try.