Normally this happens when a duplicate account exists, one with a spotify username / password and one with your facebook details.
Did you get an email receipt for your subscription purchase? In it, it shows your Spotify username:
Logout, and be sure to use it to login to your account. It's the one with the Premium features.
Hey there you,
Yeah, you! 😁
Welcome - we're glad you joined the Spotify Community!
While you here, let's have a fun game…