Opt out is the wrong word to use in this scenario.
As per @petergdownload's screenshot.
We have Lease offers and Trade up offers.
Both allow you to trade your phone in after 12 months and recontract with a brand-new handset. You do need to hand the phone back in good working order.
If you were to "opt out," you'll need to pay out the remaining cost of your handset (which may differ depending on how far into your contract) The handset subsidy would not apply.