You need to call them.
I have received email from TPG with an offer from Vodafone. They state this exclusive offer is for very few selected customers, however if you just mention this offer to Vodafone they will honour it without proof.
Each number you transfer besides the first number, they will give you 5% off each sim plan. (E.g. 2 numbers = 5% off each sim plan). Maximum is 20% off each plan.
They are very low on stock, and only have black colour in stock. Essentially, you only pay for the sim plan (cheapest plan is $40 per month, with 40gb data) and the iPhone is free.
NOTE: You do not need to be a current customer with Vodafone or TPG.
Do you have to pretend to be a TPG customer? Or what