I have their $30/5gb prepaid plan, and I didn't know this applied to me.

Their Music Freedom service allows you to stream music without it counting against your data usage. Their supported app list is still growing, too.

https://support.t-mobile.com/docs/DOC-10969

AccuRadio
BlackPlanet Radio
Digitally Imported
Fit Radio
Fresca Radio
Google Play Music
Grooveshark
iHeartRadio
iTunes Radio
JAZZRADIO
Live365
Mad Genius Radio
Pandora
radio.com
Radio Paradise
radioPup
RadioTunes
Rdio
Rhapsody
ROCKRADIO
Saavn
Samsung's Milk Music
Slacker
Songza
SoundCloud
Spotify
Xbox Music

You mean EE?

TMo and EE [and Orange] have the same parent company, but I have no idea if they offer the same services. AFAIK this is US-only