Loismustdye: I was interested if the mobile was on a contract ie, still had 18 months to go on the mobile contract and wanted a new phone. THats what happened when I upgraded my last one to the touch.
Although the mobile contract was also billed with the landline (ie only one bill) so whether that has any influence on being able to pay for the phone on the combined bill I don't know.
You can have deffered payments whether its in contract, out of contract, upgrading/replacing halfway through contract etc, doesn't matter whether it's on its own account or combined with other services. I've had it done heaps of times and there always seems to be various payment options.
However, important to note, you can only have a phone paid on your next bill or over 12 months (interest free) nothing more, nothing less.
Also, you can only have 1 lot of defferd payments going at a time. E.G if you get a nice shiny new XT phone and put it on deffered payments then decide you want another one in 5 months time, you can have it on deffered payments but the remaining payments for the old phone would be lumped up onto your next bill.