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.