A "stranger" will send me short messages on schedule, all of which are words of blessing. Every time I call, he doesn't answer.

Then you can contact him by SMS. No matter who he is or what he does, he always has the intention of sending you a message. His intention to contact him will be exposed one day and let you know who he is. Of course, it doesn't rule out that some boring people have nothing to do. As long as they don't affect your life, what does it matter to you that he is willing to waste his time and a dime?