You may want to ask in the Mechanics forum.
What exactly do you mean by "jammed?" Can you describe it in more detail? What were you doing when it jammed? Where you trying to shift both shifters at the same time?
The reason I ask is that I've done a lot of work on my bike but never worked on repairing shifter mechanics. That's an advanced topic, if you can even do it. If memory servers Campagnolo is more friendly to repairs but Shimano not as much.