If you can't access Telstra Air or Wi-fi as Jupiter suggested, if you live close to a Telstra shop you can ask if they'll let you connect to their in-store Wi-fi to do your updates.
I know of 2 Telstra shops in Adelaide that used to let customer's connect to their Wi-fi to do update. I haven't had to use it for the last couple of year's....so not sure if they still do it.
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