Hello, the CANCEL is an own transaction, so you can not access AVPs from the INVITE transaction. Refer e.g., to RFC 3261, section 9.1. Cheers, Henning From: Scherney Theodor &lt;Theodor.Scherney(a)kontron.com&gt; Sent: Donnerstag, 23. März 2023 09:37 To: Kamailio (SER) - Development Mailing List &lt;sr-dev(a)lists.kamailio.org&gt; Subject: [sr-dev] $avp(id) - AVPs - Problem Hello, http://www.kamailio.org/wiki/cookbooks/5.5.x/pseudovariables#avp_id_-_avps AVPs are special variables that are attached to SIP transactions. It is R/W variable (you can assign values to it directly in configuration file). Call scenario: Alice calls Bob. Here I set the AVP: route[REQINIT] { if (is_method("INVITE")){ $avp(ICID_AVP) = $hdr(P-Charging-Vector); } Receiving 200 Ok at onreply_route[term_reply] { } I can access the AVP. Other scenario: Alice calls Bob. Alice cancels the call. In this case I can't access the AVP. route[term_subsequent] { if (is_method("CANCEL")){ if (t_lookup_cancel()) { xlog("L_INFO", "INVITE transaction exists"); xlog("L_INFO", "ICID_AVP [$avp(ICID_AVP)]\n"); } } } 2023-03-23T09:11:56.332778+01:00 172.29.21.53 vict2-scscf[44536] - [logSDID@20306 resource="xlog"] INFO: <script>: INVITE transaction exists 2023-03-23T09:11:56.333292+01:00 172.29.21.53 vict2-scscf[44536] - [logSDID@20306 resource="xlog"] INFO: <script>: ICID_AVP [<null>] What could be the problem? Thanks! BR Theo