The service description can be found in the OICP 2.1.

Section:
3.2.2 eRoamingAuthorizeRemoteReservationStop

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/**
 * Initiate a remote reservation stop of the given charging session at the given EVSE.
 *
 * @param Timestamp The timestamp of the request.
 * @param RoamingNetworkId The unique identification for the roaming network.
 * @param SessionId The unique identification for this charging session.
 * @param PartnerSessionId The unique identification for this charging session on the partner side.
 * @param ProviderId The unique identification of the e-mobility service provider.
 * @param EVSEId The unique identification of an EVSE.
 * @return A remote stop result object.
 */
public RemoteReservationStopResult Invoke(Instant             Timestamp,
                               RoamingNetwork_Id   RoamingNetworkId,
                               ChargingSession_Id  SessionId,
                               ChargingSession_Id  PartnerSessionId,
                               EVSP_Id             ProviderId,
                               EVSE_Id             EVSEId);


/**
 * Register an event callback for incoming remote reservation stop requests.
 *
 * @param RemoteReservationStopHandler an implementation of the remote reservation stop functional interface.
 */
public void OnRemoteReservationStop(IRemoteReservationStop RemoteReservationStopHandler)
{ ... }

CPOServer HubjectCPOServer = new CPOServer(RoamingNetwork_Id.Parse("Playground"));

HubjectCPOServer.OnRemoteReservationStop((Timestamp,
                               RoamingNetworkId,
                               SessionId,
                               PartnerSessionId,
                               ProviderId,
                               EVSEId) -> {

    System.out.println("[" + Timestamp.                          toString() +
                          "] RemoteStop in '" + RoamingNetworkId.toString() +
                          "' from '"          + ProviderId.      toString() +
                          "' at '"            + EVSEId.          toString() +
                          "'");

    return RemoteReservationStopResult.Success;

});