What actions can I take about an I-do-your-homework website offering academic fraud services for money?
This is called contract cheating.  It is an old and very well known problem.
Students cannot do anything about advertisements for contract cheating.  Since the sellers are usually unaffiliated with universities, universities cannot punish them either.
If you have evidence that someone is purchasing contract cheating services, turn that evidence in to the person responsible for academic integrity at your university.