You can cancel only the tickets that were booked on RussianRailways.com. The cancellation is available in your Profile. To log in to your Profile, use the email address to which the tickets were sent.
Three steps of the cancellation process:
Cancellation policy is different for international paper tickets for Trans-Siberian, Trans-Mongolian and Trans-Manchurian trains. Information is provided upon booking. Tickets with departure from Mongolia and China are not refundable in case of cancellation, date of departure can not be changed, tickets can not be reissued if passengers provide wrong personal information upon booking (e.g. name, birth date, passport number, etc.)