Your company will have, or should have, some kind of harrassment policy. This policy will aim to protect employees and aim to create a safe and pleasant environment for all. Your actions have made the receptionist feel upset and angry, also, if you follow this up by trying to coerce her in to not going to the MD, you are in breach of policy. Now the company could be justified in using this against you and debating an appropriate punishment. Or, they may be realistic and see that this is a tupid prank that has back fired, depends on how the receptionist has been made to feel.