iPhone 5 itunes match tracks download via LTE even if set NOT to use cellular data: Apple Support Communities

Kind of a nasty bug in iOS 6, if you have a new iPhone, a lot of music, and use iTunes Match; check the link below for work-arounds until the bug is fixed

"I had exactly the same issue, iTunes was downloading tonnes of tunes from iTunes Match via the Verizon LTE network, even though I had set the settings to not download anything from iTunes over the mobile network. I spoke to a senior tech supervisor (Michael) who said he would elevate this to the engineers - he's going to call me back to let me know the outcome. I will post an update here once I've spoken to him again."

iPhone 5 itunes match tracks download...: Apple Support Communities