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Do you have a Sony device or Blackberry as that is normally associated with the later and it means no voice calls so you have either just got the phone and your number is been transferred or your phone is reported lost or stolen or you haven't paid a bill and have been cut off
Just been on the phone to a source of mine at Vodafone and it does mean your phone is blacklisted - So you have either reported is lost or stolen or you have stolen it or found it
You don't understand blocked or blacklisted - You can't make calls because it's been reported lost or stolen or you haven't been paying your bills
Then check with your provider and ask why you have the warning MM#6 or MM6 saying your phone has been blacklisted - Regardless of Vodafone or not the code is still the same