Earlier quoted context omitted.
Jenny? Don’t change your number.
It's been 41 years since the song came out. Assuming that Jenny was 21 when the song was written, (since there is a chance the number was written on a bar's bathroom wall) she would be at least 62 years old now. Statistically, there's at least a 1 in 4 chance that Jenny is dead now, and there is no chance that she didn't change her number after receiving 800 million horny crank calls.
Probably so he could rhyme 'mine' with 'nine'