How to permanently remove an unwanted device?

[#1]

I formatted my cell phone to the factory version as I do annually and a few hours after I installed spotify and connected, an Iphone connected to my spotify account, but I never had and never connected my cell phone to an iphone. The intruder kept playing music while I listened to mine, which was quite annoying. After a few minutes the intrusions stopped, but the Iphone still appears logged in with my spotify account. How to proceed?

[Vasil]

Hey there!

Sorry to see this has happened to you!

In this situation, we'd first recommend going to this page and following the instructions to log out everywhere.
After this is done, you may want to change your password and I'd recommend changing your email password as well for good measure.

This should help you out but do let us know in case the described behaviour continues.
Many thanks!