LDAP Tree 

dn: ou=contacts,dc=juliux,dc=de
objectClass: organizationalUnit
ou: contacts

dn: ou=personal,ou=contacts,dc=juliux,dc=de
objectClass: organizationalUnit
ou: personal

dn: cn=juliux,ou=personal,ou=contacts,dc=juliux,dc=de
objectClass: organizationalRole
cn: juliux

dn: uid=juliux,ou=user,dc=juliux,dc=de
objectClass: top
objectClass: person
objectClass: organizationalPerson
objectClass: inetOrgPerson
objectClass: posixAccount
objectClass: shadowAccount
uidNumber: 4001
uid: juliux
gidNumber: 4012
givenName: XXX
sn: XXX
mail: XXXX
cn: XXX
userPassword:: XXX
shadowLastChange: 15242
homeDirectory: /home/juliux
loginShell: /bin/bash

ACL's from /etc/ldap/slapd.d/cn=config/olcDatabase={1}hdb.ldif
olcAccess: {0}to attrs=userPassword,shadowLastChange by dn="cn=admin,dc=juliux
 ,dc=de" write by anonymous auth by self write by * none
olcAccess: {1}to dn.base="" by * read
olcAccess: {2}to * by dn="cn=admin,dc=juliux,dc=de" write by * read
olcAccess: {3}to dn="cn=juliux,ou=personal,ou=contacts,dc=juliux,dc=de" by dn=
 "uid=juliux,ou=user,dc=juliux,dc=de" read
olcAccess: {4}to dn="cn=juliux,ou=personal,ou=contacts,dc=juliux,dc=de" by dn=
 "uid=juliux,ou=user,dc=juliux,dc=de" write

test-contact.ldif
dn: uid=fdc6a36a7cc92974b190634b22bac1fe,cn=juliux,ou=personal,ou=contacts,dc=juliux,dc=de
uid: fdc6a36a7cc92974b190634b22bac1fe
objectClass: inetorgperson
objectClass: person
cn: Bar Foo
givenname: Bar
sn: Foo
street: Example Stree
displayname: Foo, Bar

command:
ldapadd -H ldapi:/// -xW -D uid=juliux,ou=user,dc=juliux,dc=de -f test_contact.ldif
Enter LDAP Password: 
adding new entry "uid=fdc6a36a7cc92974b190634b22bac1fe,cn=juliux,ou=personal,ou=contacts,dc=juliux,dc=de"
ldap_add: Insufficient access (50)
	additional info: no write access to parent