I did not know that yesterday!

Why are the numbers arranged differently on phones and calculators?

No one's quite certain why the numbers on phones read from top to
bottom when keyboard and calculator numbers read from the bottom up.
But there's no denying which set of buttons came first -- numeric
keypads are based on old adding machines. Generations of accountants
have used them with blurring efficiency.
So why mess with tradition? Why not keep the same format for
telephones? Fortunately, the brains at HowStuffWorks have formulated a
few theories that might explain this bizarre discrepancy.

One theory contends that prototype touchtone keypads in the '50s were
originally identical to calculator keypads, but operators were so
adept at using them they jammed the phone lines. The number layout was
redesigned to actually slow down fast fingers.

Another theory states the phone keypad came from a 1960 Bell Labs
survey in which more people liked the "1" on top (after all, we're not
all accountants). Or maybe the phone layout was roughly based on the
old rotary system.