Refunds for dissatisfied customers. What is in the law about this?

Question

Law in IT

My site presents services in the form of advertisements on its pages. Anyone can order advertising for any term without intermediaries.
Suppose the client was not satisfied and demands a refund. Based on the laws of Ukraine, the Russian Federation, during what period does the client have the right to demand a return? (return of goods in Ukraine is possible within 14 days, but I am not selling a product but a service, how can I be here?). Are there specific terms? Do I have to make a return after the expiration of the order?
Thanks to

Answer 1

there is no way to be
for the service money will not return
a specific term - "fraud"