With 10-digit strings we can distinguish roughly 10,000,000,000 phones from each other. That assumes someone can have the number 000-000-0000, which is probably God's number; and sure, maybe Satan has laid claim to 666-666-6666, so it's not available; but we're only being approximate here. The bottom line is that there's enough space in principle for everyone in the USA to have 20 or 30 different cell phone numbers, if we use it efficiently.
But we don't.
I have often stared at documents like gas bills and been amazed to see things like account numbers or other identification numbers as long as 18 or 20 digits. There are only about 7 × 109 people in the world. Some account numbers are so long you could give separate account numbers to every member of the population on a billion planets with populations like ours. Those numbers could record the addresses and ages and incomes of the customers instead of just being random digit strings. But we don't do that. The information society that people get so worried about — the world in which The Government knows all your details and tracks everything you do — hasn't arrived yet, and probably never will. We're not that organized as a species. We waste too much time and too many of our computational resources keeping track of pointless random digit strings and being unable to relate them to each other.