How difficult can it be?!

This trip is driving me MAD!!! I've been trying to book an other baggage for a month now and all the people i've been talking with told me something different. I, eventually decide to go and book it at the airport (still in advance) and they told me they could not do that, don't ask me why. Anyway i went to the Flight Centre and a really kind lady told me to call directly Quantas and make the booking by phone. After i waited 57 minutes, the call finally reached a Quantas operator that told me, paying to the extra baggage at the airport, the day of the flight, is THE ONLY WAY. Wich means that i've got to pay the double and be nervous not to get my both suitcases home until the same morning of my flight. This is so freaking annoying. I'll let you know if i get all my stuff home.