Check your itemised phone bills!!
 

I just checked my itemised phone bill (Telstra) online as I was surprised to see such a high charge for "Calls to Non Telstra mobiles". I found I was charged even for calls to mobiles that were not answered! Each call was timed - between 2 and 18 seconds:frown: Anyway, after I called and complained they promptly reversed the charges (I was imagining a huge battle ahead of me).

Similarly, TPG charged me twice for each international SMS - again charges reversed and problem rectified after I complained.

So better check your bills in detail!