You need msg_apply_changes() for each operation that alters a SIP header, if you do
another operation that is going to alter same part. Changes to headers are not applied
immediately:
*
http://www.kamailio.org/wiki/tutorials/faq/main#why_changes_made_to_headers…
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Reply to this email directly or view it on GitHub:
https://github.com/kamailio/kamailio/issues/428#issuecomment-162013783