Spring JPA Joint table

i have to map an old database to write a web service. the problem is it use the foreign key as the primerty key. and some non unique row number. then it works as a composite key. here is the class structure

@Entity
@Table(name = "AD_CLIENT")
public class Client {
    @Id
    @Column(name = "CLIENT_CODE")
    private String clientCode;
    @Column(name = "CLIENT_NAME")
    private String fullName;

    @OneToMany(mappedBy = "client",fetch = FetchType.LAZY)
    @JsonIgnore
    List<ClientTelephone> clientTelephones;
}

this is the other class

@Entity
@Table(name="AD_CLIENT_TELEPHONE")
public class ClientTelephone {
    @Id
    @Column(name = "ROW_NUMBER")
    private int rownum;
    @Column(name = "TEL_NO")
    private String telephone;
    @Column(name = "TEL_TYPE")
    private String telType;
    @ManyToOne(fetch = FetchType.LAZY)
    @JoinColumn(name = "CLIENT_CODE")
    @JsonIgnore 
    private Client client;
}

here is the data sample enter image description here

when get te data it will work as expected but when it comes to save its not picking up with foreign key. just check with id which is rownum and throws an exception

Hibernate: select c1_0.row_number,c1_0.client_code,c1_0.tel_type,c1_0.tel_no from ad_client_telephone c1_0 where c1_0.row_number=?
2022-09-23T15:32:37.051+05:30  INFO 56164 --- [nio-8080-exec-5] o.h.e.internal.DefaultLoadEventListener  : HHH000327: Error performing load command

org.hibernate.HibernateException: Duplicate row was found and `ASSERT` was specified