Hi @aka-momo
Previously we had a contact form where you could also choose to 'submit a complaint'. A while ago we stopped offering this contact option. So there is no e-mail address available unfortunately.
You can submit a complaint via customer service. This can be done, for example, by telephone, but also via Facebook, Twitter or chat. I can imagine that you may prefer to discuss the situation privately. In that situation, you could choose to send the complaint to us privately via Facebook Messenger.