I use Meizu 5. I use Unicom number. It used to be ok to send text messages. I just sent text messages on China Unicom.

1. Confirm whether the phone bill is sufficient;

2. Enter SMS, and then select "…"-> "Settings->; SMS center, to confirm whether the number of SMS center is set correctly (the specific number can be confirmed by consulting the operator);

3. Eliminate the influence of optimized management software, and restart the mobile phone to test whether it is normal after unloading;

4. Check whether there are blacklist and other related settings;

5. You can change the mobile phone cards of other operators to test whether you can send short messages normally;

6. Back up mobile phone data, refresh the latest system and clear user data.

If it still can't be solved, please back up your mobile phone data and send it for repair and testing as soon as possible.