You can't use your phone over there unless you have a very expensive GSM one. You can rent one before you go, which is what I did last year. Bit expensive though. The other option is to hire one at the aiport in the States (which I have also done), but you have to take it back to the same airport, as far as I understand. I think it worked out to be around $10 US a week to rent it..

I think you would be better to take an international phone card with you, much cheaper.

As for a coat, I have taken both a great cashmere/wool coat (cashmere is warmer and lighter than wool) and bought a great waterproof coat from an outdoor shop. At this time of the year you should be able to get a good price. If the Aussie dollar was batter, I would say wait until you get there, as I have a great coat from LL Bean, but the exchange rate makes that not as cost effective.

Good luck back-packing at that time of year. It will be very cold!

Cheers

Louise in Sydney