Hello @Ibdefaria. Thanks for posting in the Spotify Community!
This isn't cool to hear. I would agree with @Shadow9XCav that it sounds like your account was switched over to Premium for Family. Let's find out what's going on so we can get things straightened around. 🙂
If you're sure you didn't sign up for Premium for Family, I would immediately change your passwords and click the Sign Out Everywhere button on your account page to secure your account.
Next I'd cancel your Premium for Family subscriptionvia your Account Subscription page. (But only if you're not going to use the benefits of adding up to 5 additional family members to your account.) You can get in touch with Spotify Support about refunding the difference by explaining the situation to them via contact methods below:
Okay @Ibdefaria... Do you check your account on Websites? Such as PC Web? (Not the PC Spotify App) Because you might've clicked the Upgrade to Family Premium! I also think of someone accessed your device and applied the Family Premium to your account. Tell @Kirashi the whole details since he or she is a Spotify Rockstar.