I tried a free trial of Acrobat Pro in July. Still billed monthly

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.

<"moved from using the community">

you can only (correctly) cancel onceso it's not clear what you're doing that's incorrect.

in any case, you'll probably end-up needing to contact adobe support. there are 2 ways to contact adobe support; chat and twitter (now x):

chat:
if you have or want to purchase a subscription, 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.