@Hollerith 1, LucreLout
I understand what you're saying, however given this situation I would of course act in a professional manner and answer any questions or queries raised.
However, in this case, where the plan for using a temporary (expensive) ISDN line until a (cheap) broadband line is available should have been known about (and signed off) at least at the next management level up. Therefore it should not be up to James to remind them of it. At the very least accounts should be keeping an eye on it.