Daniel,   Actually, the HSS is not returning the uri with the +.  There are no users int the HSS database with a public ID with a + so the HSS returns the USER_UNKNOWN.   Looking at the PCAP, the I-CSCF sends a diameter msg to the HSS asking for the verification the public ID of: Public-Identity: sip:+alice@ims522.irisims.org <sip:+alice@ims522.irisims.org>   The diameter msg from HSS is returning : AVP: Experimental-Result-Code(298) l=12 f=-M- val=DIAMETER_ERROR_USER_UNKNOWN (5001)   Why do we want the I-CSCF to add a + to all URI’s don’t start with a +?   The I-CSCF is the module that is adding the +, assuming that we should be able to included Kamailio.cfg for respective modules, is there a directive or variable that I need to set?   Or do I simply comment out that code?   Thanks,   Martin Woscek The MITRE Corp. mwoscek(a)mitre.org <mailto:mwoscek@mitre.org> Phone: 703-983-2650 FAX: 703-983-7142   *From:*Daniel-Constantin Mierla &lt;miconda(a)gmail.com&gt; *Sent:* Tuesday, June 11, 2019 6:22 AM *To:* Kamailio (SER) - Users Mailing List &lt;sr-users(a)lists.kamailio.org&gt;rg>; Woscek, Martin W. &lt;mwoscek(a)mitre.org&gt; *Subject:* [EXT] Re: [SR-Users] Kamailio 5.2.2 ICSCF changing sip to tel   Hello, that prefix operation is done only if the r-uri username does not have +. So if you HSS is returning the r-uri with +, then all is ok, no other + is added. On the other hand, I am not sure what is the error or the issue you try to sort out. The error message is because of the xlog(...) in the config. Cheers, Daniel On 10.06.19 16:17, Woscek, Martin W. wrote: Hello all,   The HSS is responding with 604 errors when the I-CSCF checks the public identity of the caller.  PCAP attached.   It looks like our I-CSCF is modifying the sip uri’s to tel uri’s (e.164-like), referenced attached PCAP: in_uri=sip:alice@ims522.irisims.org out_uri=sip:+alice@ims522.irisims.org <mailto:alice@ims522.irisims.org>   syslog output: Jun  6 16:50:06 imskamailio /usr/local/sbin/kamailio[14066]: ERROR: <script>: $ru => sip:+alice@irisims.org   Looking at the default (out of the box) Kamailio.cfg for I-CSCF the following script snipet is where the modification to our sip URI is happening:   # -------------------------  request routing logic ------------------- # main routing logic   route{ #!ifdef WITH_DEBUG                 xlog("I-CSCF >>>>>>>>>>>>>>>>>>>> $rm $ru ($fu => $tu ($si:$sp) to $tu, $ci)\n"); #!endif   *                if !($rU =~ "\+.*") {* *                                prefix("+");*                 }   Is there a I-CSCF setting directive we missed? Or should we simply comment the above?   Any advice is appreciated.     Thanks, Martin Woscek _______________________________________________ Kamailio (SER) - Users Mailing List sr-users(a)lists.kamailio.org <mailto:sr-users@lists.kamailio.org> https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users -- Daniel-Constantin Mierla -- www.asipto.com <http://www.asipto.com> www.twitter.com/miconda <http://www.twitter.com/miconda> -- www.linkedin.com/in/miconda <http://www.linkedin.com/in/miconda>