trying to switch two VMs over to a new Size

HI All,

I am trying to switch two VMs (one for test, one for Live) to new sizes to match the reserved instance "Standard B2" West Europe. I believe I have to stop(deallocate) each VM in order to "see" all the different types of VM. But when I stop the first (Test) VM, many of the size options are greyed out, and the "Standard B2" just is not displayed at all. What am I doing wrong? Thanks