Hello, @sgp8591. Thanks for stopping by. We'll be happy to help. Spotify and iHeartradio are part of the music streaming partners and their use will not count against your data allotment as long as you are simply streaming music.
Other services like Cloud streaming, song downloads, video content, non-audio content, and other data sent by streaming partners (e.g., pic advertisements, album art) are excluded.
The device allows you to check the usage of the apps so you can keep a track, however, it should not count against the data allotment.