how to cancel my apple music membership?

If you want to cancel it simply turn off automatic subscription renewal.

You may find the instruction how to cancel it here: Manage your Apple Music membership - Apple Support

http://9to5mac.com/2015/06/30/how-to-cancel-apple-music-subscription-auto-renewa l/

If you have turned iff off - that is all you need.

You are not addressing to Apple here. Take a look at the articles above. You have already turned off automatic renewal.