I'd call and ask for her dad.
Don't tell him right off the bat who you are, the first thing out of your mouth should be "I want to help pay the phone bill I helped create, how would (insert $ amount here) be for a start, and where do I send the money order?

If he still hangs up, I'd try again in 2 weeks...then maybe once more, but if none of that works...it's over. If you know her name, she'll be 18 in a couple years and you can find eachother again then.

Best of luck!

__________________
MichaelBlue