Translated by google:
>>Unable to send SMS to a specific number from my iPhone
Hello, I am unable to send SMS messages from my iPhone. I can send messages to other contacts, but SMS messages fail to reach one specific number; I receive a "Not Delivered / Try Again" alert. I was able to send messages when I inserted my SIM card into another phone, so the issue likely lies with my iPhone. I have tried various troubleshooting steps—including checking iMessage, MMS, and network settings—and have previously contacted Apple Support, but the problem remains unresolved. Could you please check if there are any blocks or restrictions on my phone preventing SMS messages from being sent?<<
Sorry, this is a user to user community and we can't look into your personal settings.
But, have a look at the general troubleshooting for not being able to send & receive messages:
If you can't send or receive messages on your iPhone or iPad - Apple Support
iPhone veya iPad'inizde mesaj gönderemiyor ya da alamıyorsanız - Apple Destek (TR)
If you are trying to send messages to a non Apple device:
- Check your network connection. To send a message as iMessage, RCS, or MMS, you need a cellular data or Wi-Fi connection. To send an SMS message, you need cellular network connection. If you turn on Wi-Fi Calling, you can send SMS messages over Wi-Fi.
- Check with your carrier to see if the type of message you’re trying to send, like RCS, MMS, or SMS, is supported.
- If you’re trying to send group MMS messages on an iPhone, go to Settings, then tap Apps. Tap Messages and turn on Send as Text Message. If you don't see an option to turn on Send as Text Message or Group Messaging on your iPhone, then your carrier might not support this feature.
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copied from: If you can't send or receive messages on your iPhone or iPad - Apple Support
Also contact your carrier. Since SMS is a carrier service, they might be able to find the reason for that.
