Shouting at staff
You need to take this matter very seriously as it could jeopardise your future career. If this was the first instance of such behaviour, a suspension seems extreme. If you have any previous warnings on record about your conduct, this might be more understandable. Assuming this was a momentary lapse of judgment on your part, the action seems to be out of all proportion. Check that procedures were carried out properly. Even if you were unable to question the assistant, you should still have been able to point out errors in her statement as part of your own submission. In my view, any suspension should not start until all avenues for appeal have been exhausted. Consult your union's legal department or a solicitor with experience in employment law as a matter of urgency.