o2 app, number already registered

I've added a second phone (myhandy)n on a new o2 free  contact to my existing account. It's not showing up in the o2 app from my existing contract, except as a completed order. When I try to register for the o2 App with the new phone number on the new phone, it says an o2 account already exists for this number. What can I do? I'd like the app on the new phone, and was hoping, as it's another contract although paid by me, I would get a second set of o2 bonuses (I like the o2 Videobusters for example, another film per month would be great!)