It's unstated in the article, but it does say "orders of pizzas, kebabs, pittas and other food that he never ordered kept flowing in", which could mean it's a lot of different places delivering to him.

If the harasser is smart, they'd vary the restaurants and use a burst of different ones at a time in sequence, with long time gaps per restaurant.

And if the delivery driver isn't reporting it to the restaurants every time, the delivery person doesn't necessarily have a high chance of reporting it, so I see how it could continue for a while if there are a lot of restaurants in his delivery range. (Assuming it really is harassment, that is.)