Hi, I'm Ashik. Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP
If you get this message when you send, then this is not an issue with your phone. It is an issue with your carrier network or with your account. You need to call your carrier network or SIM provider and ask them to reset your account and disable SMS blocking features. If you tell me who your carrier network is, then I will send you their contact number.
To make sure this is not on their end, you can try resetting your settings. But only do this after getting confirmation from your carrier that the issue is not on their end. Go to Settings > General > Reset and tap Reset All Settings. This will reset some settings like WiFi, network settings, blocking settings etc. You need to connect to WiFi network, set your wallpaper, tones etc after resetting all settings.
Let me know the results please.