Are they asking you for 300 dollars in order to disable it? This seems illogical to me.
Checking their relevant article I see they’re asking to upgrade to premium to have it enabled, and that they offer 5 free credits:
Try letting them know once more that the feature seems to be enabled, not disabled, and ask them if they can disable it without you having to pay.
Alternatively, if you don’t want to contact their support again or they tell you they can’t do anything, setting up Cloudflare might help resolve this:
Cloudflare also offers SSL options and setting it up is quite easy, if you select the “Full” option and use a self-signed certificate, you won’t have to worry about renewals for 10 years!