The payment for the paid-for PDF is processed through Payhip. As far as I can test here in Germany no cell number is required. Maybe you trigger some extra verification that I don’t?

As for the email, I require it so that I can subscribe all of my readers to a weekly newsl… haha just joking. Juuuuust joking :-) If you try it, you will find that a bogus email address works just fine.