How do you recover your Spotify username through ITunes?

After updating my Spotify app, it signed me out of my account. Problem is, I can't remember my username or email. The only one I remember, is my older account that I do not use. I cannot for the life of me remember my username or email, but Spotify is still an active subscription through ITunes that I am currently paying for. I have tried to contact Spotify and they told me since it is through ITunes, to go to Apple Support. I am awaiting an email from an Apple Technician, but I was curious if anyone knew any steps I could take from here. Thanks in advance.