Help me figure out how to play a .wav file over a voice modem

I'm looking for a little help with modem communications. I'm trying to get a .wav file to play through a modem. What I've got is a program that has a couple buttons on it. You enter a phone number or numbers into the text box at the top, click the 'dial next' button, and the modem dials the first number in the list. Once it's connected, you click one of the next 3 buttons to play a .wav file over the modem. The connecting part works fine, but playing the .wav has been giving me a headache all day. I don't know what to do with this thing.

I'm lost. I need a little direction here so I can try to figure out where to go with this. Anyone with a little knowledge and experience, please point me in the right direction.

This program is being developed for work, as we play with VoIP phone systems all day, and make a ton of test calls to make sure they have 2 way Audio, connect to the right numbers, etc. It sure would make life a ton easier if I could figure this thing out.

Any ideas you have, send them over, even if you think they're stupid. Rest assured, I've tried more ignorant ideas on this project than you can shake a stick at, so you can't possibly come up with a bad suggestion if you try.

Thanks in advance for your help.

Mike