I want to cancel Kindel unlimited because I am being charged over $10.00 per month for unlimited and all I agreed to was the Kindle trial.

SOURCE: I want to cancel my free trial of kindle unlimited

read this Amazon FreeTime Unlimited and Kindle FreeTime Unlimited Terms Conditions
The pertinent words are " If you don't want to upgrade to a paid subscription, you can opt out at any time during the free trial period from the FreeTime section of Settings on your Kindle Fire or Amazon Fire TV" and "You may cancel your subscription at any time from within FreeTime from the FreeTime section of Settings on your Kindle Fire or Amazon Fire TV."
If these do not help you (they only give you a starting place as to where to look) then wait for a more in-depth answer or contact amazon help directly - I find chat the quickest easiest way to get help if there is going to be anything useful
8.February.2015

SOURCE: Cancel my kindle unlimited free trial

This video may help
How to Unsubscribe From Kindle FreeTime Unlimited After Trial Period
8.February.2015

SOURCE: I need to cancel Kindle Unlimited

Log into your AMAZON Account....
Under Your Account....arrow down to Your Kindle Unlimited.....and click on it.....
Go to Manage Your Kindle Unlimited Membership.
Under Manager Membership, select Cancel Kindle Unlimited Membership.
Select, End Membership on (date).

Mark Besa

• 10 Answers
• Posted on Mar 15, 2017

SOURCE: How do I cancel Kindle Unlimited

Go to Manage your Kindle Unlimited Membership under Manage Membership select Cancel Kindle Unlimited Membership then select End Membership on [DATE].