Why does my mobile phone show that the network connection is incorrect when sending a short message?

When sending a short message, it shows that the network connection is incorrect for the following reasons:

1, the local network signal is not good, try another place;

2. Check whether the calling card is loose, turn it off again and plug it in again.

If there is nothing wrong with the above, there is something wrong with the mobile phone itself.

Try to restore the factory settings first, if not, send it for after-sales maintenance.