Every operator forum has a pinned thread titled "Dispute with [operator]? Post it here". That is the right place, because it keeps the whole history in one place and on that operator's record.
Before you post, contact the operator directly and give them a chance to fix it. Most issues are resolved that way, and we will ask whether you have.
Include: what happened and the dates, any reference or ticket number, the amount if it is a payment issue, and what the operator has told you so far.
Never include: account numbers, government IDs, or screenshots showing your personal details. We remove those without warning, to protect you.
What we do. We pass the details to the operator and keep the thread open until they answer. If it cannot be resolved, we say so publicly and it is reflected in our review of them.
We are not a regulator and cannot compel anyone to pay. For the formal route, see our complaints policy.