[SR-Users] several uac_replace_from in one dialog

Hi! Making calls via different trunks through kamailio for simply so

uac_replace_from ("sip:regname@ipaddress"); if (! t_relay ()) {    uac_replace_from ("sip:regname2@ipaddress");    t_relay () } exit

and run tcpdump i see in fisrt INVITE From: "testname" <sip: regname @ ipaddress>; tag = as21aea6e0

in second INVITE From: "testname" <sip: regname @ ipaddress sipregname2 @ ipaddress>; tag = as21aea6e0

and in the log file EROOR: can not parse From URI, and then can not find a BYE to terminate the call I try do remove_hf insert_hf but then i do second remove_hf it realy not delete and i have two field From. Who can tell me how few times to change the From field in a one dialog?