Loud static coming from receiver?

[kanackattack2010]

at my business, I have a portable xm radio reciever hooked up to a sony receiver that plays the xm radio throughout the store. I recently tried to hook up the xm to play on the phone line, for when people get put on hold. I used a headphone splitter from the back of the xm receiver and have one end going to the regular, sony, receiver which plays the music throughout the store, and the other going into a telephone box. When I checked to see if it was working, I only heard an extremely loud static, and the static stays the same no matter if I change the volume. To make this situation even more weird, just to make sure the line was okay because I had soldered the wire at one point, I plugged in my iPod, and it worked perfectly. Please help me! Any suggestions are appreciated!