it may well push you over your limit though. listening is free, but it still has to be transfered to your computer which means that your ISP will be counting up the bandwidth.
If you've gone over your limit, it means you've been surfing too much. that includes listening to online radio, as most stations stream anything in between 32 and 128 kbps. bandwidth gets used up pretty quickly if you're listening to that stuff a few hours a day.