You obviously did not gain financially from your heinous crime as you paid the same rate as you otherwise would.
The offence of fraud involves a financial gain which sadly passed you by.
The company through a company officer were aware of what you proposed to do.
This is most definitely NOT fraud and I would be inclined to ask exactly how you should have acted or exactly what rule you have breached because I would put money on the fact that none of them will have a clue.
In order to commit fraud or attempt to commit the criminal offence of fraud there must be some gain.
They are accusing you of not acting honestly when the chairman knew what you were doing.
There is a world of difference between fraud and what actually happened. Some idiot has swallowed a law dictionary.
Ask them to state where in the company rules does it state that they can apply any sanction whatsoever because I bet there is not one!!
Yes, you have breached the rules but fraud is a little hysterical.
Admit a technical breach, put the mitigating circumstances, done with knowledge etc and tell them to get a life.