Premium upgraded to Family without my notice + someone playing songs

[mhls]

Plan

Will become premium next month, since I now have cancelled the family premium.

Country

 Turkey

Device

Samsung Note 4

Operating System

My Question or Issue

 I have had the spotify premium for seven months. Turns out after the first three months, it was upgraded into a famliy premium account, and I have had no knowledge of this at all.
I have no reason to believe that there has been a security leak on any of my other accounts. I have no idea how this happened.
I have now changed my spotify password. None of my other accounts got corrupted and haven't noticed anything curious about the other ones (hope).

For the last month, someone has been playing music on my spotify. The music is being played either on an "Iphone 9" device or on a "Trap House Speaker" device.
I called my friends to find out whether someones playing music on a device I previously logged onto, but no one is doing this, and I am certain about this.
Then, I proceeded to first log out on all devices through the web browser.
This didn't work, as this person continued to play music on my spotify the very next day.
Then I changed my password and logged out on all devices again. I did the logging out a lot of times, but the password change I have only done once.
This person still has access to my device.
While doing the password change, I was going through my Spotify settings and found out that I was using a family subscription. There was also another person registered as a family user on my account.
Name: Didem(not sure about the first name)
Last name: Aydın(sure about the last name)
When I saw this, I immediately removed this registration, and I didn't take time to look at or note down the credentials of this person, so I don't have any memory of the email address.

So this is the case. This person probably still has access to my account. The last they have used it is like two days ago.

I cannot understand how this serious of a leakage can happen... Spotify really should take an interest in this case.

I would be glad if anyone can help, but I think I already have followed all possible solution options that Spotify offers. It feels like this situation needs some authorized and official intervention.

One explanation is someone infiltrated my account and turned it into a family premium and then gave access to themselves.

But whatever the situation, I have removed them and have changed my password, they still have access to my spotify. 
I need help with removing them....

[Maxim]

Hi there!

Sorry to hear that you think someone else has gained access to your Spotify account. Check out this Spotify Answer for the next steps to take.

Thanks!