I just have the same exact problem. It's a bug in iOS. If you go to iTunes App on your iOS device, you will see a Downloads section. There you will see all pending iTunes Match downloads. It's a pain if you have thousands of songs to delete them from this download queue one by one. So here's how to squash this bug.
You absolutely don't need to reset your phone and go back to square one or email iTunes. Spare yourself the trouble. Here is a simple fix.
Go to Settings > iTunes & App Store > iTunes Match
On that screen, turn iTunes Match off.
Tap your Apple ID on that screen and tap Sign Out. (I don't know if this is necessary but it works anyway. Just an added precaution for this to work.)
Restart your iOS device (Hold down Sleep and Home button for about 5 seconds until it goes black and the apple logo in a black background appears).
Go back to iTunes Store > Downloads and voila they're all gone. All those pending downloads are reset. And your iOS device won't download anymore of those songs unless you tell it to.