You can't send text messages if you change your mobile phone card.

1. According to the information you provided, if your mobile phone can't send short messages, you can try to restart or replace your mobile phone for testing, and check whether the following conditions exist:

1 SMS center number is set incorrectly, please re-enter the correct SMS center number;

2 No signal or insufficient battery power;

3. Because the system is busy during the holiday short message sending peak period, it is suggested that you try again later or avoid the sending peak period;

4 The sending format is incorrect. If you send a short message to PHS users, you need to add the area code before the number;

5 SMS sending time exceeds 24 hours;

6. The mobile phone shields the short message sending function;

7 blacklisted by SMS;

The balance of number 8 is insufficient;

9 SMS Inbox and Outbox are full.

2. If this is not the case, it is suggested that you can contact Unicom's manual customer service for verification. The actual situation is subject to local policies.