Before you write anything: make absolutely certain it has stopped. People discover a bill, spend two hours composing a support ticket, and the meter is still running the whole time. That is a bad sequence and it also undermines the request.
So, in order, and this takes twenty minutes:
Find the exact resource and turn it off. Not scale it down: off, unless you know precisely what you are doing.
Check for siblings. Whatever you created, check whether the same mistake exists in another region, another project or another environment. Duplicates across regions are extremely common and easy to miss, because most consoles show you one region at a time.
Verify from the billing side, not the console. Look at the current period's accruing charges and confirm the line has flattened. A resource can look deleted and still be billing.
Then screenshot everything, the resource, the deletion, the cost graph showing when it started and when it stopped.
That evidence is what your request is built on, and it is also what tells you whether the number is final or still growing. Then write the message, with the situation already contained.