I've seen comms from AGL that fit this need, though I can't recall all circumstances. For example, I received an email with the subject "Important information about your energy rates", but the body only referred changes to my gas rates. Be specific at all times, unless it is impossible to be so. So the above should have been "Important information about your gas rates". Another example would be "here are the details of your new energy plan with us", which then said "welcome to your new energy pl ...