Spotify on iOS uses Mobile Data when logged on to WiFi (iPhone 4S, iOS6.02)

[frededk]

Hi,

our daughter has a 6Gb Mobile Data plan - and it seems that after updating to iOS6 her iPhone is now using Mobile Data even when logged on to our WiFI - and also when she's in school and logged on to the schools WiFi?

Of course if she shuts off Mobile Data on iOS then no data traffic is used on 3G.

We have reinstalled her iPhone completely and tried only to have Spotify installed. And even then when Spotify is playing - it is using 3G data traffic?

She has been using Spotify since january and is loving it...But now she has to remember shutting off Mobile Data when she is on WiFi - and it should not be the case.

She has shut off Synch when on 2G/3G and also all Social Information on Spotify has been shut off - without any result!

How can this be?