I would advise against making a bunch of calls – it will be considered spam and an annoyance rather than anything positive.  Just make one call (or perhaps another one in response to the finale if you called before) and be positive – don't be aggressive or negative or abusive of ABC, don't call them names or tell them they'd be stupid to cancel or whatever, be nice, it will have much more impact than people creating a nuisance.

There's also already a thread about how people can get in touch with ABC.

being agressive doesn't equal being angry so I wasn't meaning to imply you were saying people should be angry.  But being agressive by calling repeatedly won't help – that was the point I was trying to make.  One really positive call will make up for a bunch of annoying calls from the same person – remember, there is administration involved on their end to deal with the calls and someone having to go through a bunch of calls from the same person may get well annoyed by it

Do you have skype?  I used skype to call and didn't even think about it being an issue calling from outside the US (though I should have assumed it'd be like that! always is)

You may need to turn the microphone boost up – you can do that through the SOUND options in the control panel (assuming you're using windows) – you could probably do a search on "boost microphone level" online for specific instructions how to do it