There are lots of "radio" apps that stream, but none work like a real radio, with the exception of Tune-In Radio. Most are designed to stream only from certain servers where they have collections of popular music, not listen to radio with real humans playing the music and announcing things.
As for 2 GB, I stream a couple hours a day on average and I rarely get close to 2 GB monthly data use. One way to hold it down is to select streaming radio stations that stream at different bandwidths and give you the option of which to connect to. For example, my favorite is KQAC, which offers 32k and 64k streams. If I was afraid of hitting my data limit I'd choose the 32k stream.