eldap interface, invoking modify function

How to invoke modify function of eldap module? For example, lets consider mod_vcard_ldap.erl. Examining eldap/eldap.erl and mod_vcard_ldap.erl files I've done it in following way:

eldap:modify("mod_vcard_ldap",
"CN=unit, DC=my, DC=domain",
[eldap:replace("attr",["value"])] )

While execution error arise:

E(<0.263.0>:gen_iq_handler:67): {undef,
[{eldap,replace,["attr",["value"]]},
{mod_vcard_ldap,my_function,3},
{mod_vcard_ldap,process_sm_iq,3},
{gen_iq_handler,process_iq,6},
{gen_iq_handler,queue_loop,3},
{proc_lib,init_p,5}]}

This piece of code executed somewhere after eldap:start_link("mod_vcard_ldap",...) in the module mod_vcard_ldap.erl.

Thanks.