SMS not working.

Hello everyone, (sorry for my english), I've got a problem with my iPhone 6, 16 GB, iOS 8.4.

When I send a SMS to another person that doesen't use iMessage the text "Not delivered" appears. In addiction, the person receives 3 SMS.

I read and I did every passage that is described in Apple's support: I checked my device settings, I checked the recipient's contact info, I deleted existing conversations, I restarted my device and check for updates, I turned iMessage off and than on, I signed out and than in to iMessage and FaceTime, I reset my network settings, I restored my device.

So, I can't understand what is the problem.
If anyone knows an answer I would be grateful.

Greetings.