I can't rename my transaction on HP Virtual User Generator Script

I can't rename my transaction which is on this function:

lr_start_transaction((char*)MDM_GET_ASSOCIATIONS);

and this the script where she is coded:

//########## start the test scenario ############
web_set_max_html_param_len("8000");
web_set_sockets_option("SSL_VERSION", "TLS");
web_add_auto_header("Content-Type","application/xml");
web_add_auto_header("Accept","application/json");
web_add_auto_header("Authorization",lr_eval_string("{AUTHORIZATION}"));

//GetAssociations, NOTE: our dummy customers have often NO associations!
web_reg_save_param("RESPONSE", "LB=", "RB=", "Search=Body", LAST);
lr_start_transaction((char*)MDM_GENERIC_TRANSACTION);
lr_start_transaction((char*)MDM_GET_ASSOCIATIONS);
web_custom_request(MDM_GET_ASSOCIATIONS, 
    "URL={TEST_ENV_HOSTNAME}/api/v3/clients/{BUSINESS_CONTEXT}/customers/{GCID}/associations",
    "Method=GET", 
    "Resource=1",   // => We are retrieving a ressource, 
                    // which implies that it is not critical for the success of the script. 
                    // Any failures (HTTP 404 - Not found etc.) in downloading the resource 
                    // will be considered as warnings rather than errors.
    "EncType=application/xml", 
    "Referer=Loadrunner",
    LAST);
lr_end_transaction((char*)MDM_GET_ASSOCIATIONS, LR_AUTO);
lr_end_transaction((char*)MDM_GENERIC_TRANSACTION, LR_AUTO);

return 0;

}