How to Contact Support for Membership Refund?

Hi, I had downgraded my account to individual seller straight after signing up? However Amazon has charged the monthly fee. Is there anyway to contact Amazon to ask for refund .I didn’t do any activity on the account at allnwith Pro access and it was downgraded straight away. I can’t find a way of taking up this cse with Amazon as it only redirects to forums and help topics. Unfortunately, the account switching (downgrade ticket) is closed more than 10 days ago and it doesn’t allow me to report the issue on the same Case ID.I am new to this, can anyone give a tip how to get in touch with Amazon, how to open case with Amazon, in general, even if needed in future.