Hello, pbx -> kamailio -> provider kamailio registers (uacreg) on provider. When I call through my provider I need to change headers To From and PAI. I tried with uac_replace_from and uac_replace_to. $tU for example 0987656789 if($fU=~"1234567") { uac_replace_from("sip:provider_login@provider.com"); uac_replace_to("sip:$tU@provider.com"); } My provider answers on Invite with 183 progress, so pbx answers with PRACK. Kamailio change To and from like this: To: <sip:0987656789@provider.comsip:0987656789@provider.comTo: <sip:0987656789@provider.comsip:0987656789@provider.com> From: <sip:provider_login@provider.comsip:provider_login@provider.com From: <sip:provider_login@provider.comsip:provider_login@provider.com> Is it a bug? I tried to disable this modification for PRACK u REQINIT ($csb != "2 PRACK") It haven't worked for me. I solved this issue with this code. remove_hf("From"); if ($ft == $null) { insert_hf("From: <sip:provider_login@provider.com>\r\n", "To"); } else { insert_hf("From: <sip:provider_login@provider.com>;tag=$ft\r\n", "To"); } version: kamailio 5.7.0-dev0 (x86_64/linux) Ubuntu 18 -- Regards, Alex