Hi mahmood164,
You've done a great job troubleshooting this issue. Try quitting the Messages app following these steps: How to force an app to close on your iPhone, iPad, or iPod touch.
Once it's closed, restart your iPhone with these steps: Restart your iPhone.
After restarting, launch Messages, and try again with your contact. If the issue persists, delete the contact from your iPhone, then add their information back in, try sending a message again. If you're still unable to send only to this contact, verify with your carrier that there is no "block" in place from the carrier side. Because this is only occurring with an SMS message, it's going through your carrier's network. The iMessage messages go through the Apple network. This article will give you more information about the 2 types of messages: About iMessage and SMS/MMS.
Enjoy the day!