Return Trip
In most cases, CitizenPlane is the company selling only one flight of your booking, unless shown otherwise on your personal space at https://mytrip.citizenplane.com/ (using your PNR and Last Name).
For any queries regarding your other flight, you will need to contact your Travel Agent (OTA) directly. To find out more about your OTA, please see the following article: https://help.citizenplane.com/article/19-who-is-my-travel-agent