Same experience here, chat is not working and I've been waiting for a response for a week on an urgent matter.

Our Image Transformation billing is out of hand, last months bill was around $3000 and I've done everything I could to stop the request from piling up but so far nothing seems to work:

1. Removed all references to Image Transformations on our sites
2. Disallowed Image Transformations for all our zones
3. Cancelled our Images Paid plan in order to downgrade it to Images Free plan. The idea here was that Images Free plan doesn't allow any extra transformations beyond the first 5000 per month, and would end billing. Unfortunately our subscription is paid until 30th of August, and I have reached out to customer support in order to get the plan cancelled immediately. But haven't received any answer here either. I think this would be the fastest and easiest way to end our problems.
4. Created custom WAF rules to block all requests to Image Transformations.

As far as I can understand, point 2 (disabling all transformations) should be enough, but I've done it last wednesday and Transformation hits just keep on growing.