Xiaomi's mobile phone 4 has a full signal, but it can't make calls or send text messages.

The common reasons why mobile phones can't answer calls and their solutions are as follows:

Method 1: check whether the mobile phone is in arrears, and suggest paying for recharging;

Method 2: Check whether the mobile phone is set with call forwarding, airplane mode on and call barring. It is recommended to cancel and try again.

Method 3: check whether the function or signal of the mobile phone is normal, and suggest changing the mobile phone or trying again;

Method 4: If roaming to other places can't be used, it is recommended to check whether the local network signal is normal and whether roaming permission is enabled for this number;

Method 5: try to restart or replace the mobile phone to see if you can answer the phone;

Method 6: Take the mobile phone card to the local business hall for testing or replacement.

The processing method that the mobile phone cannot send short messages is as follows:

Method 1: You can change your mobile phone and see if you can send and receive short messages.

Method 2: If you can send and receive short messages, I suggest you plug the card back into your mobile phone and send yourself a short message to see if you can receive it.

Method 3 If not, I suggest you check whether there is a problem with the sim card;

Method 4: Check whether the number of SMS center is set correctly;

Method 5: Take the mobile phone card to the local business hall for testing or replacement.