I signed up for a free trial, not a monthly subscription. I was unaware that I would be billed. I did not provide my payment information to pay for this plan, you simply used my general Adobe CC billing info. I expect this plan to be cancelled at no cost to me and a refund of these monthly fees.
Seems link you signed up for '10 free stock images' offer. With this offer, you are signing up for an annual plan of 10 assets/month where the first month is free and you can cancel risk-free within the first month if you do not wish to continue with the subscription.
In order to cancel the subscription:
You may also Contact Customer Care for help regarding cancellation and billing related issues.
Hope this helps!