Yeah you're getting them 10 new customers. That is 10 new contracts. Of course. They should give you the iPhone for free. Heck maybe two iPhones.
If you can actually get 10 new people to sign up for a new contract per person then more power to you. It really isn't that great of a deal if you think about what you actually are doing. They are pretty much giving you an iPhone (which you still have to spend money on) for getting them 10 new contracts.
Not anything worth celebrating.
P.S. what does "top up" mean? Sounds like they have to sign up for a higher contract as well.
EDIT: I now know that top up means add to your SIM card, therefore it seems this may be a little better deal then once thought.