Hi, and welcome to the community!
Please note it can take some time for premium to activate across all devices.
1) Have you checked your Subscriptions page to make sure you are successfully on the trial?
2) Try logging out/in and reinstalling Spotify.
3) Make sure you're logging in with the right account; it's very easy to have both facebook and Spotify details!
If it still isn't working, submit an online contact form; and someone at Spotify can look into it for you.
If you get an automated reply; make sure to reply to it directly (even if it's from a no reply); and it will be sent to the Spotify staff.
Anthony