Have you ever created more than one account by using a different email address ?
Firstly check all your playback devices with the NowTV App on it and under the My Account section of the App it should show the email address that you signed into the devices with (just in case one of the devices is using a different email address).
Also check all your email addresses for any NowTV correspondence (including junk and deleted folders).
Should you manage to find another account, then cancel the passes on it.
With regards to a refund you will need to contact NowTV live chat where they should also be able to help in tracking down any additional accounts created by you in the past.
Open the link below, then select the most appropriate category, then pick the nearest help topic, then move towards the bottom of the screen and click the green arrow underneath "How to Get in Touch" to show the live chat button.