Completely agree with uber here. Talk to them, if they don't budge, keep bugging them about it once every week or so. If they haven't budged by the time your exams come around, quit at the last possible moment.
You won't get in trouble for bringing up issues like that, management might not be too thrilled to hear about it, but they won't punish you for it, your exams were planned well ahead of this rota, and you made them aware of the dates.