It's also strongly advised that you change the password for:
The email address associated with your Spotify account (e.g. with Gmail, Hotmail, etc.).
Any Facebook profile associated with your Spotify account. You can make sure you're the only one currently logged into your Facebook in your Facebook Settings, under Security and login > Where You’re Logged In.
Any service where you use the same password as Spotify.
If after that the issue persists, you can reach out to Customer Support. You can find the contact form here.