Data use in offline mode

[Sebke]

Hi, I've started using spotify in my car through bluetooth connection with my iPhone. It appaers that even when I'm in offline mode spotify still uses data and it seems to me more then it should. I've read around that a small amount of data is still being used (albumcover and connection) but here I'm talking about around 200Mb for 30-40 minutes of listening. That seems and awfull lot. Does any one has got an explanation for this? And what could I do to solve this?

I know I can cut off the data use of spotify but still it would be nice not having to switch it on and off each time.

Thanx