I do not need the service and I only wanted to try it.

You have a 14 day grace period to cancel without penalty. 

After 14 days there's a 50% early termination fee on annual subscriptions.

But there's no penalty fee for cancelling a month-to-month plan.

Your online account

https://account.adobe.com/plans

How do I Cancel my Subscription?
https://helpx.adobe.com/manage-account/using/cancel-subscription.html
===============
Subscription & Cancellation Terms:
https://www.adobe.com/legal/subscription-terms.html

CONTACT ADOBE SUPPORT:
================
Online Chat: https://helpx.adobe.com/contact.html?rghtup=autoOpen
Twitter: https://twitter.com/adobecare

make sure you're aware of the cancellation terms by selecting your plan type (at the top of the page here), https://helpx.adobe.com/manage-account/using/creative-cloud-subscription-terms.html

for info on how to cancel your subscription, this page describes the few steps involved, https://helpx.adobe.com/manage-account/using/cancel-subscription.html

if you want to cancel but are unable to follow the steps described in the "how to cancel page", contact adobe support.

there are 2 ways to contact adobe; chat and twitter (now x):

chat:
use a browser that allows popups and cookies, and click here, https://helpx.adobe.com/contact.html?rghtup=autoOpen
in the chat field (lower right), type AGENT
be patient, it can take quite a while to reach a human.

twitter/x:
tweet @AdobeCare

p.s. if you're contacted by anyone (via email or private message), it's much more likely to be a scammer than an adobe representative.

Please note that this is mainly a user-to-user forum, with only a limited amount of Adobe Employees present. We are not able to help you directly with any billing, account or subscription issues. You will need to contact Adobe Customer Care for assistance:

• https://helpx.adobe.com/contact.html?rghtup=autoOpen

The link above will open a chat window. Type "Agent" into the chat box to bypass the chatbot and get connected to a real person. (Alternatively, write to AdobeCare on X.)