I tried to register but I received a notification that my email address is already in use.

That’s odd! There are two possibilities:

1. Maybe your partner or a family member accidentally registered using your email address because you can only register once with the same email address.
2. If this is not the case your email address may have been used without authorisation. Send an email to privacy@Q8smiles.be (Belgium) or q8smiles.lu (Luxembourg).