when can I cancel my Adobe Stock subscriptions free of charge if I'm past my year of use but starting a new one? At the moment I can't afford such high fees, my financial situation has deteriorated.
Cancellation free of charge is possible during the last month of the annual subscription. If you cancel anytime, you have to pay half of the remaining dues as an early termination fee. When you cancel, you lose all accumulated and unused credits!
In your case, I would contact Adobe customer care and see what they can do for you. I would warn you, however, that when you accept a couple of free months, the paid subscription gets only paused, not cancelled.
Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers need to be disabled, you need to accept cookies! If the chat window fails to open, or is non-responsive, use a different device and/or browser to start the interaction.
For support via Twitter:
(see also here: https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 or here
Important: Adobe does NOT contact you unsolicited by e-mail or direct message. If you get contacted by direct message from a person, claiming to be an Adobe employee, look at that profile and look, if they bear the “Adobe Employee” marking under their name. Adobe support does not use Skype to give you support.
If in doubt, ask the forum.