I ordered a domain and after that I changed my mind; what do I do?

A domain does not have to be used. They can be parked for the period for which it was paid. Unfortunately, the whole domain system is based on prepaid registration and the paid money cannot be refunded. You must cancel the automatic renewal so that it is not updated at the end of the period for which you paid.
And for .ro domains, the process was updated a few years ago to an annual payment.