Getting constraint violation exception on deleting parent although i used cascadeType.all

Question

As per my requirement I have two entities company and contact which are associated with @onetomany mapping and I want to delete the company and its related contacts with it. I have used the Cascade.All but still I am getting the constraint violation exception whenever I try to delete a company.

Model :

company
-------
private List<Contact> contact;
@OneToMany(fetch = FetchType.LAZY ,mappedBy="company",cascade=CascadeType.ALL,orphanRemoval=true)

public List<Contact> getContact() {
    return contact;
}

public void setContact(List<Contact> contact) {
    this.contact = contact;
}

contact
-------
private Company company;    
@ManyToOne
@JoinColumn(name = "company_id")
public Company getCompany() {
return company;
 }

public void setCompany(Company company) {
this.company = company;

I am getting the following exception :

ERROR SqlExceptionHelper:146 - ERROR: update or delete on table "company" violates foreign key constraint "fk_6jbjhtdw6ak2in3ln4tlxm0dm" on table "contact" Detail: Key (id)=(71) is still referenced from table "contact". org.hibernate.exception.ConstraintViolationException: could not execute statement at org.hibernate.exception.internal.SQLStateConversionDelegate.convert(SQLStateConversionDelegate.java:129)