Well, I might give a few pieces of advice here, as I'm in the mood ...
Be polite to Centrelink staff. Grit your teeth and try your best. Easy enough to say, I know, and I nearly lost it yesterday with them, but it doesn't help. The department is understaffed, has a high staff turnover rate, most are not well trained, and there is little job satisfaction. If YOU are polite and maybe smile at them, they will be more inclined to help YOU.
If you can't be polite, then you can nominate another person to speak on your behalf. This can be a friend, relative, or someone from a community legal centre.
Take notes when you talk to them in person. If you are on the phone, ask for a Receipt Number. Both these actions will inspire the staff to be more accurate in the information they give you.
If you are not happy with the information you get, check it. Ring the Call Centre without giving your name and ask them the same questions. Check the Centrelink website which has heaps of information on it.
If you are not satisfied by a decision Centrelink has made about you, appeal it. Ask for a review by an Authorised Review Officer (ARO, pronounced arrow). If you still aren't happy, then you can appeal their decision to the Social Security Appeals Tribunal, and then to the Administrative Appeals Tribunal.
This publication is great. It contains heaps of information on Centrelink payments and is moderately understandable.
Keep all documents from Centrelink. I filled my garage, converted my wine cellar, stuffed the spare room, and am currently renting another house to store my rapidly increasing documentation. Take notes of conversations, as I said above.
One lovely thing about their website is that you can now upload documents online ... this means that you can reduce the number of visits to their office. No more waiting and less frustration.