"I’ve contacted them but they didn’t get back to me" -- you need to phone them up and speak to someone. Don't try to do time-sensitive stuff like this by email.
If you get this arranged in advance, then it will make things much easier on the day as they should have the required items put to one side with your name on them.
If you do have to arrange things on the day, then make sure you get to the robing area as early as you can.
Try and phone their office on Saturday morning; it's possible that there will be someone in. Otherwise, phone first thing on Monday morning.