Clicking the link below will direct you to the Spotify website and cancel your Spotify Premium trial immediately. I repeat, it will cancel immediately, so if you are logged in and you click the link, that means you just cancelled.
If you're not looking to cancel and just want some information about Spotify, here are some useful links.
To just view your Spotify account info go here.
There's also the customer services contact form.
I don't know how long these links will stay valid and if they will work in all countries in all circumstances (e.g. for Facebook and non-Facebook connected accounts) please let me know if they don't work for you and say what country you are in.