Hi, and welcome to the community!
If this is a subscription:
1) Go to your subscriptions page
2) Click on 'view your options' at the bottom of the page uunderneath 'manage your subscription'.
3) Scroll to the bottom of the next page, and click 'continue with cancellation'.
4) Follow the steps to cancel your subscription.
If you want to delete your whole account:
Firstly, theres no need really, as it's free so you can still listen to music without being charged, but if you want to leave:
You can submit an online contact form; and someone at Spotify can delete the account.
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.
This post was by Taylor - I do not work for Spotify! If this solved your issue - Mark it as a solution! If you like my post - Please add Kudos! || Spotify Profile - Taylor | Feel free to PM me - Here ||