Untitled Poem

Suppose you learned that phone numbers by formulas were made:
The cosine of your birthday or some similar charade
That turned some facts about you into digits one could call
To get you on the phone. Could this math work for all?
The birthday paradox explains the answer’s flatly no:
Ten thousand phones might have a chance; a million’s a no-go.
But maybe, then your facts and mine the same ten digits yield,
The number-allocators bump me to the next free field.
Then anyone can call me thus: they math, then place the call
If it’s not me, they just add one; repeat til on the ball.