Sometimes when I use the word "nochmal" in a more formal context such as a business e-mail, it is corrected to "noch einmal", e.g.
Ich werde ihn nochmal Anfang Oktober anrufen.
However, the sentence:
Ich werde ihn noch einmal Anfang Oktober anrufen.
sounds to me as if I am just going to call him one more time and that's it, as in the English example of a parent saying to a child "You do that one more time and...".
Is the first sentence correct formal German, and if not, what is a better way to express "again" without implying that it will be the last time?