That is something you should have checked at the time, perhaps you wanted the faster upload speed that Infinity 2 gives you?
You should not be charge for Infinity now.
I have asked a moderator to provide assistance, they will post an invite on this thread.
They are the only BT employees on this forum, and are based in the UK.
Was your bill produced before you moved home or before your orders completed? The bill may have been produced before the package changed. That should mean that, on your next bill, you would see a refund for the Unlimited Infinity 2 package back to the date that you moved and a new charge for your copper or ADSL broadband service.
If you need it looked into urgently contact our billing team at: Billing Live Chat
Let me know how you get on.