You can't send text messages if you put a phone number that you haven't used for a long time in your Apple phone.

It may be that the SMS service center is not set up or set up incorrectly.

Apple's mobile phone can't send short messages, which may be because the flight mode is turned on, or the mobile phone is in arrears, or the mobile phone is in the signal blind area of the operator, or the surrounding mobile phone signals are blocked, resulting in unsuccessful sending. IPhone can't send text messages It may be that the SMS service center is not set or set incorrectly, which makes it impossible to send SMS. This situation is very common.

If the SMS center number is wrong, you will not be able to send SMS. The solution is as follows: call the customer service phone of the local operator, ask what the number of the SMS service center is, and then set it. If it doesn't work after setting, try to restore the network settings. The network settings are as follows: Open iPhone settings, and then click General, Restore, and Restore Network Settings.