I did the chat, and asked to "change my HD package". My idea is that the old packages are no longer available, so any package added today would have the Free Platinum. The first rep said that the new HD package was "unavailable". I had him check and he came back later and said he was sorry, but could not do it.
I disconnected, got a new rep, and this guy knew exactly what I was trying to do (Classic CS Rep Roulette !) In a few minutes, I was changed from the old "Dish Latino Max HD Ultimate" (which was $20 per month) to the new "Dish Latino Max HD & Platinum" (which is $10 per month). It took only a few minutes for my Online Account Programming to reflect the change.
The rep said no fees, but it takes 24 hours for billing to be reflected online, so I will check tomorrow to see whether he actually reversed the downgrade charge (if any).
So, do not argue with your rep if they do not understand, just politely disconnect and reconnect (be sure that the name of the rep is not the same the second time to ensure that you did not end up with the same guy).
PS Interestingly, the English Language Web Page about Dish Latino has the new changes, but the Spanish Language Web Pages have not changed at all, so clearly the Spanish speaking web guy does not work weekends.