How to get rid of the red exclamation mark in short messages?

The process of deleting a message with a red exclamation mark is as follows:

Tools/materials: iphone 12, ios 15.

1. First, open the settings of the mobile phone and click the information option.

2. Then close the key to the right of iMessage option and restart.

3. Then restart the Apple phone.

4. Wait for the Apple phone to turn on again, and then click the information icon.

5. Finally, send the unsent message, and the red exclamation mark of the short message will be removed.