As per my earlier explanation this agent wasnt following the correct process. We cant hold availability for both economy and business, we can only hold availability if its for a different flight.

So i think the person you spoke to, thought they would have to hold in business class instead of your original economy booking class. If they made this mistake unfortunately yes it would have overwritten the booking class that was saved.

However they could still send the booking to ask what the price would be to upgrade without holding business availability.