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### Description I'm running Kamailio 5.2.0, whenever I relay an invite via Kamailio, my original contact header is changed from the original: sip:+XXXXXXXXX@YYY.YYY.YYY.YYYY:5060;transport=udp;gw=netvision To sip:YYY.YYY.YYY.YYY;line=sr-.n274i0TMfsHMcCAlVyAMV5IlgCXvV8n4edQlgIUlgKQ4Vk74gI1LmZ69NM79FZAR3JC.cDNLfHUj3Wnp3MP9nd*. Even when I set it correctly on my route, using: remove_hf("Contact"); append_hf("Contact: sip:$tU@YYY.YYY.YYY.YYY:5060;transport=udp;gw=netvision\r\n", "Contact"); It still ends up being modified. What can I do to keep the contact header as it is? <!-- Explain what you did, what you expected to happen, and what actually happened. -->

### Troubleshooting

#### Reproduction

<!-- If the issue can be reproduced, describe how it can be done. -->

#### Debugging Data

<!-- If you got a core dump, use gdb to extract troubleshooting data - full backtrace, local variables and the list of the code at the issue location.

gdb /path/to/kamailio /path/to/corefile bt full info locals list

If you are familiar with gdb, feel free to attach more of what you consider to be relevant. -->

``` (paste your debugging data here) ```

#### Log Messages

<!-- Check the syslog file and if there are relevant log messages printed by Kamailio, add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site). -->

``` (paste your log messages here) ```

#### SIP Traffic

<!-- If the issue is exposed by processing specific SIP messages, grab them with ngrep or save in a pcap file, then add them next, or attach to issue, or provide a link to download them (e.g., to a pastebin site). -->

``` U YYY.YYY.YYY.YYY:5060 -> 81.24.193.248:5060 INVITE sip:+442033202609@81.24.193.248:5060 SIP/2.0. Record-Route: sip:YYY.YYY.YYY.YYY;r2=on;lr=on;ftag=mp0S9yH11vryH;vsf=AAAAAAAAAAAAAAAAAAAAAAADCAEACRgPGB8AAy4xNjM-. Record-Route: sip:2YYY.YYY.YYY.YYY;line=sr-.n274V8TlidQMVyUlg87vV8nlfDXlVHB9VD0.VHB9VDoLGtNRbH7ltlTEkyQl3jXEky1LNMoRkt5ukt5ukt5ukt5ukt5ukt5ukt5ukt5W8M5WktckoLuWAsduktTMm64pCAD. Via: SIP/2.0/UDP YYY.YYY.YYY.YYY;branch=z9hG4bK53e9.308596b23ed683368534c9d609dce0f6.0. Via: SIP/2.0/UDP YYY.YYY.YYY.YYY;branch=z9hG4bKsr-kA2uvfsUlerJWtIylgCXvV8n4edQlgIUlgKQ4Vk74gI1.oJVjb2njburlgCXvV8n4edQlgIUlgKQ4HWsRbWPLVDX.GrXLcAHlcC74nZXKbTVpcHh4b6mMGZvJgLsLcJTkgtGu2PGgy**. Max-Forwards: 67. From: +18702935016 sip:+18702935016@YYY.YYY.YYY.YYY;tag=mp0S9yH11vryH. To: sip:+442033202609@81.24.193.248. Call-ID: !!:jbkfMgyHjbsDjblfjqAQlVldvgyHKolDlcIHlcknKVIdjcIT. CSeq: 18182498 INVITE. Contact: sip:YYY.YYY.YYY.YYY;line=sr-.n274i0TMfsHMcCAlVyAMV5IlgCXvV8n4edQlgIUlgKQ4Vk74gI1LmZ69NM79FZAR3JC.cDNLfHUj3Wnp3MP9nd*. User-Agent: FreeSWITCH-mod_sofia/1.9.0+git~20180706T160334Z~de3df8dc0e~64bit. Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY. Supported: timer, path, replaces. Allow-Events: talk, hold, conference, refer. Content-Type: application/sdp. Content-Disposition: session. Content-Length: 224. Remote-Party-ID: "+18702935016" sip:+18702935016@YYY.YYY.YYY.YYY;party=calling;screen=yes;privacy=off. .. v=0. o=FreeSWITCH 1585439298 1585439299 IN IP4 ZZZ.ZZZ.ZZZ.ZZZ. s=FreeSWITCH. c=IN IP4 ZZZ.ZZZ ```

### Possible Solutions

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### Additional Information

* **Kamailio Version** - output of `kamailio -v`

``` version: kamailio 5.2.0-dev6 (x86_64/linux) c4daee flags: STATS: Off, USE_TCP, USE_TLS, USE_SCTP, TLS_HOOKS, USE_RAW_SOCKS, DISABLE_NAGLE, USE_MCAST, DNS_IP_HACK, SHM_MEM, SHM_MMAP, PKG_MALLOC, Q_MALLOC, F_MALLOC, TLSF_MALLOC, DBG_SR_MEMORY, USE_FUTEX, FAST_LOCK-ADAPTIVE_WAIT, USE_DNS_CACHE, USE_DNS_FAILOVER, USE_NAPTR, USE_DST_BLACKLIST, HAVE_RESOLV_RES ADAPTIVE_WAIT_LOOPS=1024, MAX_RECV_BUFFER_SIZE 262144 MAX_URI_SIZE 1024, BUF_SIZE 65535, DEFAULT PKG_SIZE 8MB poll method support: poll, epoll_lt, epoll_et, sigio_rt, select. id: c4daee compiled on 15:59:42 Aug 22 2018 with gcc 5.4.0

```

* **Operating System**:

<!-- Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...; Kernel details (output of `uname -a`) -->

``` Linux version 4.4.0-98-generic (buildd@lcy01-03) (gcc version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.4) ) #121-Ubuntu SMP Tue Oct 10 14:24:03 UTC 2017

Linux kamaillioegress 4.4.0-98-generic #121-Ubuntu SMP Tue Oct 10 14:24:03 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

```