refund hd movie rental that won't play

We're staying with relatives in a different country. We downloaded an HD movie rental, but their TV isn't HD and it refuses to play. It's a holiday weekend, so there aren't any humans at tech support for 48 hours (and an email won't take any less time) and the rental period expires in 23 hours. We only found out that it wouldn't play after we had already started trying to play it. Can we swap the HD rental for an SD rental and watch the movie, or do we have to just bite the bullet and get charged for both and try to sort it out after the holiday weekend is over? We've already spent enough time fighting this that it's going to be bedtime before we actually get to watch anything, which pretty much *****.