There is stuff in the Yuno terms and conditions about accepting that a smart meter will be installed and possibly that it is "activated" (haven't checked in detail) but it sounds like you may have inadvertently agreed to the "activation" (from MCC02 to MCC12) even if you understood that it would remain on MCC02?
I still maintain that the CRU, ESB Networks, individual providers and the media have made a complete hames of explaining the details of smart meters to consumers giving rise to confusion like this. As I mentioned elsewhere "activation" seems to mean different things in different contexts (and may have three different potential meanings).