Query to find customer dunning contact email id

 SELECT
    account_number    account_number,
    obj.party_name    customer_name,
    sub.person_first_name,
    sub.person_last_name,
    sub.party_name    contact_name,
    LISTAGG(hcp.email_address, ',') WITHIN GROUP(
        ORDER BY
            hca.cust_account_id
    )                 emild_list,
    hrr.responsibility_type
FROM
    apps.hz_cust_accounts     hca,
    apps.hz_parties           obj,
    apps.hz_relationships     rel,
    apps.hz_contact_points    hcp,
    apps.hz_parties           sub,
    hz_cust_account_roles     hcar,
    hz_role_responsibility    hrr
WHERE
        hca.party_id = rel.object_id
    AND hca.party_id = obj.party_id
    AND rel.subject_id = sub.party_id
    AND rel.relationship_type = 'CONTACT'
    AND rel.directional_flag = 'F'
    AND rel.party_id = hcp.owner_table_id
   -- and hca.account_number=  '752588'
    AND hcp.owner_table_name = 'HZ_PARTIES'
    AND hcar.cust_account_id = hca.cust_account_id
    AND hcar.party_id = rel.party_id
    AND hrr.cust_account_role_id (+) = hcar.cust_account_role_id
    AND hrr.responsibility_type = 'DUN'
    AND hcp.contact_point_type = 'EMAIL'
GROUP BY
    account_number,
    obj.party_name,
    sub.person_first_name,
    sub.person_last_name,
    sub.party_name,
    hrr.responsibility_type

Query to get the party role for the service contract

 SELECT
    okh.id,
    okh.contract_number,
    okh.contract_number_modifier,
    okh.authoring_org_id,
    hp.party_name,
    hp.party_number,
    hca.account_number,
    flv.meaning,
    okr.rle_code
FROM
    okc_k_party_roles_b   okr,
    okc_k_headers_all_b   okh,
    hz_parties            hp,
    hz_cust_accounts_all  hca,
    fnd_lookup_values     flv
WHERE
        okr.chr_id = okh.id
    AND okr.jtot_object1_code = 'OKX_PARTY'
    AND okh.contract_number = '111111111'
    AND okr.object1_id1 = hca.party_id
    AND hp.party_id = hca.party_id
    AND okr.rle_code = flv.lookup_code
    AND flv.lookup_type = 'OKC_ROLE'
    AND trunc(nvl(flv.end_date_active, sysdate)) >= trunc(sysdate)
    AND flv.enabled_flag = 'Y'
    AND flv.language = userenv('LANG')
    ;