Reported speech or no?

Why in the sentence like this:"John called and told me he is on his way.He should be here soon",-there is no the reported speech, and the verb"is"doesn't change from the present tense form into the past simple form "was" though the word "told" denotes speaking and stands in the past form?

Even though the telephone call from John has ended and so is in the past, it would seem from the sentence that he is still presently on his way. It is quite correct to say:

John called (past) and told (past) me he is (present) on his way.

Saying that he was on his way would be grammatically correct, but it would mean that his journey was over, or that there was some doubt over it.