Welcome to the Community
I just want to make sure I completely understand this. Are you looking to do a handset upgrade on your account and get a subsidy on a new phone?
Also, you have mentioned having an unlocked phone but a Plus7 plan. Is that because you are under an agreement that hasn't finished yet? If that's the case, you can still upgrade your phone, however, the remaining subsidy would need to be paid first.
Let me know. Once I have more details, we'll be able to take it from there